Electron, X-rays, Dual Nature of Light & Matter

Transcription

1 Electron, X-rays, Dual Nature of Light & Matter Choose the correct answers :. In an evacuated tube, in which a high potential difference is applied across electrodes, the colour of positive column depends on () potential difference across the electrodes () nature of the gas in the evacuated tube nature of material of the electrodes (4) all the above. Which of the following phenomena can be explained by the wave model of light, but not by the particle model? () Pressure is exerted by a light beam () ll of the energy emitted by an atom as light can later be completely transferred to another atom light beam changes direction when passing from one medium to another (4) Light can reach the geometrical shadow of an obstacle in its path 3. When an electron moving at a high speed strikes a metal surface, which of the following is not possible? () The entire energy of the electron may be converted into an X-ray photon () ny fraction of the energy of the electron may be converted into an X-ray photon The entire energy of the electron may get converted to heat (4) The electron may undergo elastic collision with the metal surface 4. Which of the following particles is stable? () Proton () -meson Neutron (4) None of these 5. The phenomenon of photoelectric emission was discovered by () Heinrich Hertz () J. J. Thomson Maxwell Plank (4) lbert Einstein 6. If electron is moving with a velocity of.8 times the velocity of light, its mass will increase by nearly () 8% () 73% 67% (4) 33% 7. Two conducting plates and parallel to each other are held at potential and V, respectively. n electron moves from plate with a kinetic energy E. when it reaches, its kinetic energy is 3 E/. Thus the value of V is () E / (e) () E / e E / e (4) E / (e) 8. Photoelectric effect supports quantum nature of light, because (tick mark the wrong statement) () there is a minimum frequency of light below which no photoelectrons are emitted () the maximum kinetic energy of photoelectrons depends only on the frequency of light and not on its intensity even when the metal sur face is faintly illuminated, the photoelectrons leave the surface immediately (4) electric charge of photoelectrons is quantised 9. K.E associated with an electron, having de roglie wavelength of nm, is () 9. ev () 6.63 ev.5 ev (4).5 MeV. Light of = 5 nm falls on a material with a photoelectric work-function of.9 ev. Stopping potential for the most energetic emitted photoelectrons is ().65 V ().54 V.95 V (4).59 V. In a mass-spectrograph, an ion of mass number 4 and charge +e and ion of mass number and charge + e, both enter the same magnetic field with the same velocity. If the radius of circular path of is 4 cm, then the radius of circular path of is () cm () cm cm (4) 4 cm. In order to give velocity of 6 6 ms to electrons of mass 9. 8 g, these should be accelerated through a potential difference of () 6 V ().4 V 3 V (4) 9. V 3. The magnitude of specific charge on proton in S.I. system of units is ().96 8 () (4) When electrons, accelerated through a potential difference of 4 V, pass through a medium containing electric field of intensity V cm and magnetic field of intensity G, these go undeviated. The velocity of the electrons is () 5 ms () 3 ms 3 km s (4) 4 km s 5. What electric field intensity can just support a water droplet of diameter 6 m, carrying a charge of electrons? [7]

2 Electron, X-rays, Dual Nature of Light & Matter ().6 3 V m () 3. 4 V m 5. 4 V m (4) V m 6. Two similar metal plates, each of area, are arranged horizontally, one vertically above the other, a distance d apart. They are maintained at a steady potential difference V. The capacitance between them is C. The charge on the top plate is Q. small oil drop of radius r and carrying a charge q is between them. The electric force on the oil drop may be found from () q, Q and V () C, d and Q d, q and V (4) C, q and Q 7. In a Thomson s set-up for determining e/m, the same high tension dc supply provides potential to the anode of accelerating column, as also to the positive deflecting plate in the region of cross fields. If the supply voltage is doubled, by what factor should the magnetic field be increased to keep the electron beam undeflected? () () 4 (4) 8. The deflecting plates in a Thomson s set up are 5. cm long and.5 cm apart. The plates are maintained at a P.D. of 4 V. Electrons, accelerated to an energy of. kev, enter from one edge of the plates, mid-way, in a direction parallel to the plates. Deflection produced in the path of electron, till these reach the other end of the plates, is ().5 mm () 5 mm 4 mm (4). mm 9. n electron and a proton are projected in an electric field, at right angle to the field with the same velocity; then () trajectory of both the particles will be equally curved, because charge on both is same () trajectory of electron is more curved trajectory of proton is more curved (4) curvature of trajectory becomes more curved if electric field intensity is less. The maximum velocity with which an electron is emitted from a photocell is ms. The stopping potential for the electron is () 38.5 V () 36.8 V 48. V (4) 8.8 V. Calculate the velocity of electron at which its momentum is same as that of photons of wavelength of 7333 Å (h = Js and m e = 9 3 kg). () 3 ms ().5 3 ms.66 3 ms (4).9 3 ms. stream of electrons moving with a velocity of 6 7 ms passes between two parallel plates. The electric field between the plates is of intensity 3 V cm. The strength of the magnetic field, to be crossed with the electric field, required to keep the electrons undeflected is ().5 gauss ().5 gauss.5 gauss (4).5 gauss 3. n electron beam has K.E. equal to ev. If h = Js, the wavelength associated with the electrons is ().6 Å ().9 Å. Å (4). Å 4. If electron of mass 9 3 kg possesses a momentum of 6 4 kg ms, then kinetic energy associated with it is () 5 ev () 5 ev 34 ev (4) 8 ev 5. n electron, moving with a speed of.5 7 ms is deflected by an electric field of 6 Vm, perpendicular to its circular path. If the radius of the electron trajectory is.3 m, then e/m for the electron would be ().698 C kg ().76 C kg.589 C kg (4).83 C kg 6. bulb of 6 W emits monochromatic waves of wavelength 6 nm. The number of photons emitted by the lamp per minute is (h = Js) () 9 () (4) The mass of a photon in motion is h () zero () c hc (4) h c 8. The momentum of a photon of wavelength 4 Å is ().66 6 Ns ().66 7 Ns. 6 Ns (4). 7 Ns 9. The sun delivers about.4 kw/m of electromagnetic flux to the earth s surface. On a roof of dimensions 8 m m, force of radiations, assuming the roof to be a perfect absorber, is nearly () N () N N (4) none of these [8]

3 Electron, X-rays, Dual Nature of Light & Matter 3. oth proton and elecron have wavelength of Å. The ratio of energy of proton to that of electron is ().836 () (4) proton and an alpha particle are accelerated through the same potential difference. The ratio of de roglie wavelength of the proton to that of the alpha particle will be () : () : 8 : (4) : 3. Which of the following is not correct about photons? () Momentum of photon is h/c () Rest mass of photon is zero photon of fixed energy travels with same speed in all the media (4) Photons are electrically neutral 33. photon and an electron have same de-roglie wavelength. From this information, which one of the following statements is incorrect? () oth have equal momentum () Photon is travelling faster than electron Electron has greater energy than photon (4) Photon has greater energy than electron 34. If a photon of energy E has velocity c and frequency, then which one of the following represents its wavelength? () hc/e () h/ c h/ c (4) h 35. n electron at rest is accelerated through a potential difference of V volts such that a wavelength of Å is associated with it. Value of V is about () volt () 3 volt 5 volt (4) 3 volt 36. The number of photons of wavelength 498 nm, emitted by per second by a 5 W source, is about (h = Js) () () (4) beam of electrons is moving in a region having electric field of intensity Vm and magnetic field of intensity 3 T, at right angle to each other, and these two fields produce no deviation in the path of motion of electrons. If the electric field is made is zero, then radius of orbit in which the beam will move in the magnetic field would be () cm () 5.68 cm cm (4) cm 38. The K X-ray emission line of tungsten occurs at =. nm. The energy difference between K and L levels in this atom is about ().5 MeV (). MeV 59 kev (4) 3.6 ev 39. n oil drop of charge Q and of mass m falls with terminal velocity v. What should be the magnitude of vertical electric field intensity so that the drop rises upwards with the same velocity v? () mg/q () mg/q mgv/q (4) mgv/q 4. Wavelength of neutron at 7ºC is. The wavelength of neutron at 97ºC is () / 3 () / / 4 (4) / 3 4. The wavelength associated with neutrons of mass.67 7 kg and moving with velocity 4 ms is nearly (). Å (). Å 3.9 Å (4).4 Å 4. charged oil drop in Millikan s experiment remains suspended in a uniform electric field of intensity V cm. If mass of drop is 8 6 kg and g = ms, then number of excess electrons on it is () 5 () 5 (4) In a Millikan s oil drop experiment, an oil drop is subjected to a horizontal electric field of intensity NC and the drop, moves with a constant velocity, making an angle of 45º with the horizontal. If weight of the drop is W, then electric charge, in coulomb, on the drop is () W / () W W/ (4) W 44. charged oil drop falls under gravity with a terminal speed v. The oil drop is held stationary by applying suitable electric field, in a Millikan s set-up, and is found to carry excess electrons. Suddenly, the drop is observed to move upwards with terminal speed v. This means that the oil drop has picked up () 6 more electrons () 4 more electrons more electrons (4) more electron 45. Tick-mark the correct statement : () the current in a photocell increases with increase in frequency of incident light () the photoelectric current is proportional to the applied voltage across the plates of a photocell [9]

4 Electron, X-rays, Dual Nature of Light & Matter the photoelectric current increases with the increase in intensity of incident light (4) the stopping potential increases with the increase in intensity of incident light 46. In Millikan s oil drop experiment an oil drop of radius r and charge Q is held in equilibrium between the plates of a charged parallel plate capacitor when the potential difference is V. To keep a drop of radius r and with a charge Q in equilibrium between the plates the potential difference V required is () 4 V () V V (4) 8 V 47. In Millikan s oil drop experiment, a charged drop falls with a terminal velocity v. If an electric field E is applied vertically, then it starts moving in upward direction with terminal velocity v. If magnitude of electric intensity is decreased to E/, then its terminal velocity will become ().5 v () v.5 v (4).75 v 48. metal is bombarded with ultraviolet radiation of wavelength Å. The work function of the metal is ev. The kinetic energy of the photo-electrons emitted is () about ten electron-volts () about million electron-volts about one electron-volt (4) none of these 49. The work functions of the following metals are Na :.9eV, K :.5 ev, Mo : 4.7 ev, Ni : 5 ev If radiations of wavelength 33 Å from a He-Cd laser placed m away fall on the surface of above metals, then photoelectric emission would not take place from the surface of () Na () Mo, Ni K, Mo, Ni (4) any of these 5. In an experiment on photoelectric effect, the slope of the cut-off voltage versus frequency of incident light is found to be x. If Planck s constant is Js, then value of x is ().55 5 Vs () 4. 5 Vs Vs (4) none of these 5. If wavelength of incident radiations is, then stopping potential of photoelectrons is V. If the wavelength of radiations is increased to 3, then stopping potential decreases to V. The work-function of the metal, on the surface of which radiations fall, would be (). ev ().5 ev. ev (4).5 ev 5. The work function of a substance is 4. ev. The longest wavelength of light that can cause photoelectron emission from this substance is approximately () 54 nm () 4 nm 3 nm (4) nm mw of 4 Å light is directed at a photoelectric cell. If. percent of the incident photons produce photoelectrons, the number of photons emitted per sec by light source is () 6 () 4 3 (4) Two separate monochromatic light beams and of the same intensity are falling normally on a unit area of metallic surface. Their wavelengths are and, respectively. ssuming that all the incident light is used in ejecting the photoelectrons, the ratio of the number of photoelectrons from the beam to that from is () ( / ) () ( / ) ( / ) (4) ( / ) 55. For a certain metal = and the electrons come out with a maximum velocity of 4 6 m/s. If the value of = 5, then the maximum velocity of photoelectrons will be ().6 7 m/s () 8 6 m/s 6 m/s (4) 3. 7 m/s 56. Photons of energy ev and.5 ev successively illuminate a metal surface of work function.5 ev. The ratio of maximum speeds of emitted electrons is () : () : : 4 (4) : The maximum velocity of an electron emitted by light of wavelength incident on the surface of a metal of work function, is (h = Planck s constant, m = mass of electron, and c = speed of light) () ( hc ) m ( hc ) m / / () (4) ( hc m ) ( h ) m / / 58. Given that a photon of light of wavelength Å has energy.4 ev. When light of intensity I and wavelength 5 Å falls on a photo cell, the saturation current and stopping potential are.4 and.38 V, respectively. The work function is []

5 Electron, X-rays, Dual Nature of Light & Matter ().43 ev (). ev.36 ev (4).47 ev 59. In photoelectric effect experiment stopping potential is plotted along y-axis and frequency along x-axis. Then dy/dx gives the value of () h () h/e h/em (4) me/h 6. In photoelectric effect when photons of energy h fall on a photosensitive surface (work function h ) electrons are emitted from the metallic surface with a kinetic energy. It is possible to say that () all ejected electrons have same kinetic energy equal to (h h ) () the ejected electrons have a distribution of kinetic energy from zero to (h h ) the most energetic electrons have kinetic energy equal to h (4) all ejected electrons have kinetic energy h 6. Radiations of wavelength 6 Å fall on a metal plate. If work function of metal plate is.8 ev, then maximum kinetic energy that may be associated with emitted photoelectrons is (h = Js) ().68 ev ().68 ev.386 ev (4).46 ev 6. When a certain metallic surface is illuminated with monochromatic light of wavelength, the stopping potential for the photoelectric current is 3V. When the same surface is illuminated with light of wavelength, the stopping potential is V. The threshold wavelength of this surface for photoelectric emission is () 4/3 () 6 3 (4) When a surface is irradiated with a light of wavelength 58 Å, a photo current appears which vanishes if a retarding potential greater than.6 V is applied across the photo-tube. Work function of the emitting surface is nearly (h = Js) ().74 ev ().7 ev.6 ev (4).34 ev 64. The kinetic energy of most energetic electrons emitted from a metallic surface is doubled when the wavelength of the incident radiation is reduced from 4 nm to 3 nm. The work function of the metal is (). ev () 3. ev.9 ev (4).95 ev 65. metal surface is illuminated alternately by photons of energy.5 ev and.5 ev, respectively. The work function of the metal is.75 ev. The ratio of maximum energies of photoelectron in the two cases in () : 3 () : : 4 (4) : Two identical metal plates show photoelectric effect. Light of wavelength falls on plate and falls on plate, and =. The maximum kinetic energies of the photoelectrons in the two cases are, respectively, k and k. Which one of the following statements is true? () k = k () k = k k < k / (4) k > k / 67. In a photocell, with wavelength, the fastest electron has speed v. If the exciting wavelength is decreased to.75, then the speed of the fastest emitted photoelectron will be ().75. v () 4/3. v less than 4 /3. v (4) greater than 4/3. v 68. Which of the following is dependent on the intensity of incident radiation, in a photo-electric experiment? () mount of photoelectric current () Stopping potential Maximum K.E. of photoelectrons (4) None of these 69. The minimum frequency of radiations of a light source, to eject photoelectrons from the surface of material of work function ev, is ( h = Js) () Hz () Hz Hz (4) Hz 7. Ultra-violet waves of wavelengths 8 Å and 7 Å, when allowed to fall on hydrogen atoms in their ground state, are found to liberate electrons with maximum K.E..8 ev and 4. ev, respectively. From this information, value of h is found to be () Js () Js Js (4) Js 7. Monochromatic X-rays, when reflected from a crystal surface with lattice spacing. Å, produce first order diffraction maximum at = 3º. The wavelength of X-rays is (). Å (). Å 4. Å (4).5 Å 7. In ragg s experiment, Davisson and Germer used electrons as incident radiations on the plane of nickel crystal. If lattice space between the crystal layers is.96 Å and the angle of grazing for maximum of first reflection pattern is 6º, then wavelength associated with the electrons is []

6 Electron, X-rays, Dual Nature of Light & Matter ().83 Å ().66 Å 3.3 Å (4) 6.6 Å 73. In an experiment on photoelectric emission by -rays on tungsten, one of the peak in the energy distribution is at 35 kev for M-shell electron. The binding energy in the M-shell is 5 kev. The wavelength of -rays is nearly () 3. m () 3. m 3. m (4) 3. 9 m 74. n X-ray tube has a short wavelength end at.45 Å. Then voltage across the tube is nearly () 45 V () 96 V 76 V (4) 66 V 75. Percentage of energy of fast moving electrons, converted into X-rays in X-ray tube, is about () % () %.% (4).% 76. In a Coolidge tube, the potential difference across the tube is kv, and m current flows through the voltage supply. Only.% of the energy carried by the electrons striking the target is converted into X-rays. The X-rays beam carries a power of (). W () W. W (4) W 77. White X-rays are called white because () these are produced most abundantly in X-ray tubes () these are electromagnetic waves and hence have a nature similar to white light these can be converted to visible light using coated screens, and these affect photographic plates, just like light (4) these have a continuous range of wavelengths 78. The minimum wavelength of X-ray that can be produced in a Coolidge tube depends on () the metal used as the target () the intensity of the electron beam striking the target the current flowing through the filament (4) the potential difference between the cathode and the anode 79. The minimum wavelength of X-ray produced at accelerating potential V is. If accelerating potential is changed to V, the minimum wavelength would become () 4 () / (4) /4 8. If a potential difference of, volts is applied across an X-ray tube, the cut-off wavelength will be () 6. m () 6. m 6. m (4) 3. m 8. If the potential difference applied across a Coolidge tube is increased, () the wavelength of the K line will increase () the wavelength of the K line will decrease the difference in wavelength between the K and K lines will decrease (4) none of the above 8. When a beam of accelerated electrons hit a target, which one of the following wavelengths is absent in the continuous spectrum of X-rays, if the X-ray tube is operated at 4, V? (i).5 Å (ii). Å (iii).35 Å (iv).4 Å (). Å only (). Å and.5 Å only. Å,.5 Å and.35 Å only (4) Waves of all the above wavelengths 83. The largest distance between interatomic planes in a crystal is 9 m. The upper limit for wavelength of X-rays which can be studied with the crystal is () Å () Å Å (4) 5 Å 84. X-rays are used to irradiate sodium and copper surfaces in two separate experiments and stopping potential determined. This stopping potential is () equal in both the cases () greater for sodium greater for copper (4) infinite in both cases 85. When a metal of atomic number Z is used as the target in a Coolidge tube, let be the frequency of the K line. Corresponding values of Z and are known for a number of metals. Which of the following plots will give a straight line? () against Z () against Z against Z (4) against Z 86. If 6% of the energy supplied to an incandescent W bulb is radiated out as visible light of average wavelength of 55 nm, then the number of photons emitted per second by the bulb is nearly ().66 9 () (4) Electrons with energy 8 kev are incident on the tungsten target of an X-ray tube. K-shell electrons of tungsten have 7.5 kev energy. X-rays emitted by the tube contain only []

7 Electron, X-rays, Dual Nature of Light & Matter () a continuous X-ray spectrum (remsstrahlung) with a minimum wavelength of ~.55 Å () a continuous X-ray spectrum (remsstrahlung) with all wavelengths the characteristic X-ray spectrum of tungsten (4) a continuous X-ray spectrum (remsstrahlung) with a minimum wavelength of ~.55Å and the characteristic X-ray spectrum of tungsten 88. charged particle with specific charge s moves undeflected through a region of space containing mutually perpendicular and uniform electric and magnetic fields, E and. When the E field is switched off, the particle will move in a circular path of radius () E s Es () Es E (4) s 89. When a photon is incident on an electron, supposed to be perfectly elastic, the photon is not annihilated. The phenomenon associated with this case is called () photo-electric effect () Compton scattering thermionic emission (4) Rayleigh scattering 9. Which of the following is wrong about Compton scattering? () Unlike in photoelectric emission, electron here is elastic in nature () The phenomenon proves particle nature of light The increase in wavelength of scattered photon is given by the relation ( angle of scattering and h m is mass of electron) ( cos ) mc (4) Photon here is not fully absorbed as in case of photoelectric emission 9. photon of wavelength 5 nm stops a moving hydrogen atom of mass.66 7 kg. The velocity of hydrogen atom before collision with the photon is (Take h = Js) () 4. ms () 6.4 ms.6 ms (4) 3. ms 9. When photons of energy 4.5 ev strike the surface of a metal, the ejected photoelectrons have maximum kinetic energy T (expressed in ev) and de roglie wavelength. The maximum kinetic energy of photoelectrons liberated from another metal by photons of energy 4.7 ev is T = (T.5 ev). If the de roglie wavelength of these photoelectrons is =, then work function of metal and T are, respectively, () W =.5 ev and T =. ev () W =. ev and T =.5 ev W =.75 ev and T =.5 ev (4) W =.5 ev and T =.75 ev 93. In the above question, work function of metal and T are, respectively, () T =.5 ev and W = 3.45 ev () T =. ev and W = 3.7 ev T =.5 ev and W = 3. ev (4) T =.5 ev and W = 4. ev 94. In a photoelectric effect set-up, a point source of light of power 3. 3 W emits mono-energic photons of energy 5. ev. The source is located at a distance.8 m from the centre of a stationary metallic sphere of radius.8 3 m. If the efficiency of emission of photoelectron is one in every 6 incident photons, then the number of photoelectrons emitted per second is S.8 m () 6 s () 5 s 3 s (4) 4 s 95. proton of mass.67 7 kg is accelerated, from rest, through a potential difference of V volts. Wavelength associated with the proton would be.9.48 () Å () V.87 Å V (4) V.93 Å V 96. The intensity of X-rays from a Coolidge tube is plotted against wavelength as shown in the figure. The minimum wavelength found is c and the wavelength of the K line is K. s the accelerating voltage is increased I C K [3]

8 Electron, X-rays, Dual Nature of Light & Matter () K C increases () K C decreases K increases (4) K decreases 97. photon and an electron of mass m have same energy. If p and e are the wavelengths associated with the photon and the electron, respectively, then / is equal to e p h h () () mc mc h h (4) mc 4mc 98. Inside the deflecting plates of length L, in a Thomson s set-up, electrical field has intensity E. Electrons, accelerated to an energy of ev, enter from one edge of plates midway, in the direction parallel to the plates. The linear deflection produced in the electrons, while crossing the plates, would be () EL /V () EL /V EL /V (4) EL /4V 99. If V is the accelerating potential difference in X-ray tube, then the minimum possible wavelength of X-rays produced is () 43 Å V 43 Å V () (4) 443 Å V 443 Å V.If specific charge of electrons is.76 C kg, then the total momentum of electrons in a straight wire of length. m, carrying a current of 4.4, is ().5 9 Ns ().5 Ns Ns (4) 4.4 Ns [4]

9 tomic & Nuclear Physics Choose the correct answers :. and are isotopes. and C are isobars. ll three are radioactive (), and C must belong to the same element (), and C may belong to the same element it is possible that will change to through a radioactive decay process (4) it is possible that will change to C through a radioactive decay process. In the following nuclear reaction, K is He 4 + Z X Z+ Y K () electron () proton neutron (4) positron 3. The mass density of a nucleus varies with its mass number as proportional to () () / (4) º 4. Diameter of nucleus of aluminium atom of atomic mass 7 is about ().7 fermi () Å.45 5 m (4) m 5. Ratio of nuclear radii of Cs 35 to Ca 4 is : ().4 ().5.75 (4).5 6. ccording to Yukawa theory, the nuclear forces between the nucleons act through the exchange of () positron () -meson k-meson (4) -meson 7. If the average mass of a proton and a neutron is.66 7 kg and R (radius of hydrogen nucleus) is. 5 m, then nuclear density is about ().3 8 kg m 3 () kg m kg m 3 (4).9 7 kg m 3 8. Which one of the following is not correct in ohr model of hydrogen atom? () The radius of nth orbit is proportional to n () The total energy of electron in nth orbit is proportional to n The angular momentum of the electron in an orbit is an integral multiple of h/ (4) The magnitude of the potential energy of an electron in any orbit is greater than that of its total energy 9. Which of the following statements is not true about the nuclear force? () Its range is very small () It is an exchange force with -meson as the exchange particle It is an exchange force with electron as the exchange particle (4) It is much stronger than electromagnetic as well as gravitational force. Out of three isotopes H, H and H 3 of hydrogen, () all are stable () two are unstable H 3 decays to H (4) H 3 decays to He 3. If element with principal quantum number n > 4 were not allowed in nature, the number of possible elements would be () 6 () 3 4 (4) 64. The angular speed of electron in the nth orbit of hydrogen atom is () directly proportional to n () directly proportional to n inversely proportional to n 3 (4) inversely proportional to n 3. Diameter of third orbit of hydrogen atom is about () 3.8 Å ().95 nm 4.8 Å (4).64 nm 4. How many times does the electron go around the first ohr orbit of hydrogen in a second? () () (4) Which of the following combinations of radioactive decays results in the formation of an isotope of the original nucleus? () One alpha particle and two gamma rays () Two beta particles and one alpha particle Two beta particles and two alpha particles (4) One alpha particle and four beta particles 6. In the decay process 9 U 38 9 Th 3, () 4 -particles and -particles are emitted () -particles and 4 -particles are emitted 4 -particles and 3 -particles are emitted (4) -particles and -particles are emitted 7. What is the S.I. unit for measuring the amount of radioactivity? () curie () becquerel rutherford (4) roentgen 8. One Rutherford is () 3.7 disintegrations/sec () disintegrations/sec 6 disintegrations/sec (4) disintegration/sec [5]

10 tomic & Nuclear Physics 9. Maximum binding energy per nucleon is for () lead () platinum iron (4) cobalt. During a negative -decay, () an electron, already present in the nucleus, is ejected () a proton in the nucleus decays to form a neutron, emitting an electron a neutron in the nucleus decays to form a proton, emitting an electron (4) after the emission of -particle, extra energy is emitted in the form of an electron. The manifestation of band structure in solids is a consequence of () Heisenberg s uncertainty principle () Pauli s exclusion principle ohr s correspondence principle (4) Ohm s law e. What are the dimensions of symbols have usual meanings? () M L T () M L T M L T (4) M L T hc, where 3. The ends and of a metallic wire car ry radioactive substances, emitting -particles and -particles at the same rate. Pick the correct statement. Emitter Emitter () There is no current between and () There is current from to. There is current from to. (4) There are two currents one from the middle of the wire to and the other from the middle of the wire to. 4. sodium atom of mass kg, initially at rest, emits a photon of yellow light of wavelength 6 Å, and recoils in the direction opposite to the direction of emission of photon. The recoil velocity of sodium atom is (take h = Js) ().4 ms ().9 ms 3.4 ms (4).9 ms 5. n electron of mass 9 3 kg revolves in a circular orbit of radius.53 Å, around the nucleus of hydrogen atom with a velocity of. 6 ms. From this given information, value of Plank s constant is () Js () Js Js (4) Js 6. When an electron-positron pair annihilates, the energy released is about ().8 3 J ().6 3 J 3. 3 J (4) J 7. n electron in a hydrogen atom makes transition from n = n, to n = n such that its time period of rotation in n is 8 times that in n. Then, the possible values of n and n may be () n = 4, n =, or n = 3, n = () n = 4, n =, or n =, n = n = 5, n =, or n = 4, n = (4) n = 6, n =, or n = 4, n = 8. The electron in a hydrogen atom makes a transition from an excited state to the ground state. Which of the following statements is true? () Its kinetic energy increases and its potential and total energies decrease () Its kinetic energy decreases, potential energy increases and its total energy remains the same Its kinetic and total energies decrease and its potential energy increases (4) Its kinetic, potential and total energies decrease 9. hydrogen atom in an excited state emits a photon which has the longest wavelength of the Paschen series. Further emissions from the atom cannot include the () longest wavelength of the Lyman series () second longest wavelength of the Lyman series longest wavelength of the almer series (4) second longest wavelength of the almer series 3. Whenever a hydrogen atom emits a photon in the almer series, () it may emit another photon in the almer series () it must emit another photon in the Paschen series the second photon, if emitted, will have a wavelength of about nm (4) it may emit a second photon, but the wavelength of this photon cannot be predicted 3. n electron with kinetic energy = E ev collides with a hydrogen atom in the ground state. The collision will be elastic () for all values of E () for E <. ev for E < 3.6 ev (4) only for E < 3.4 ev [6]

11 tomic & Nuclear Physics 3. Let the potential energy of a hydrogen atom in the ground state be zero. Then its energy in the first excited state will be (). ev () 3.6 ev. ev (4) 7. ev 33. When a hydrogen atom emits a photon in going from n = 5 to n =, its recoil speed is closer to () 4 ms () ms 4 ms (4) 8 ms 34. Let be the frequency of the series limit of the Lyman series, be the frequency of the first line of the Lyman series, and 3 be the frequency of the series limit of the almer series () = 3 () = 3 3 = ( + ) / (4) + = When a hydrogen atom emits a photon of energy. ev, its orbital angular momentum changes by ().5 34 Js (). 34 Js Js (4) Js 36. photon of energy. ev corresponds to light of wavelength. Due to an electron transition from n = to n = in a hydrogen atom, light of wavelength is emitted. If we take into account the recoil of the atom when the photon is emitted, () = () < > (4) the data is not sufficient to reach a conclusion 37. n orbital electron in the ground state of hydrogen has an angular momentum L, and an orbital electron in the first orbit in the ground state of lithium has an angular momentum L () L = L () L = 3L L = 3L (4) L = 9L 38. When white light (violet to red) is passed through hydrogen gas at room temperature, absorption lines will be observed in the () Lyman series () almer series both () and () (4) neither () or () 39. If radiation of all wavelengths from ultraviolet to infrared is passed through hydrogen gas at room temperature absorption lines will be observed in the () Lyman series () almer series both () and () (4) neither () or () 4. The penetrating powers of, and radiations, in decreasing order, are (),, (),,,, (4),, 4. When, and radiations pass through a gas, their ionizing powers, in decreasing order, are (),, (),,,, (4),, 4. hydrogen-like atom has one electron revolving around a stationary nucleus. The energy required to excite the electron from nd to 3rd orbit is 47. ev. The atomic number (Z) of the atom is () 3 () 4 5 (4) More stable nuclei have the mass number near to () 3 () (4) The ionization energy of hydr ogen atom is 3.6 ev. Following ohr s theory, the energy corresponding to a transition between the 3 rd and the 4 th orbit is () 3.4eV ().5eV.85eV (4).66 ev. 45. Fusion reaction takes place at high temperature because () atoms are ionized at high temperature () molecules break up at high temperature nuclei break up at high temperature (4) kinetic energy is high enough to overcome repulsion between nuclei. 46. s expected from classical mechanics, a free particle of mass m, confined to a line of length L, can have following sets of energy, except (h is Planck s constant) h () 8m L h m L 9 h () 8m L h (4) 4m L 47. The ratio of the energies of the hydrogen atom in its first and second excited states is () /4 () 4/9 9/4 (4) If the wavelength of the first line of the almar series of hydrogen is 656 Å, then the wavelength of the second line of the series should be () 8857 Å () 38 Å 486 Å (4) 454 Å 49. The figure indicates the energy levels of a certain atom. When the system moves from E to E level, a photon of wavelength is emitted. The wavelength of photon produced during its transition from 4E/3 to E level is [7]

12 tomic & Nuclear Physics E 4E/3 E () /3 () 3/4 4/3 (4) 3 5. The de roglie wavelength of an electron in nth ohr orbit of an atom is related to the radius r of the orbit as () = r/n () = n.r = n/r (4) = nr/ 5. Which of the following is a pair of isodiaspheres? () 9 U 38 and 9 Th 34 () 88 Ra 36 and 86 Rn 3 6 C 4 and 8 O 6 (4) 6 C 4 and 7 N 4 5. If m p =.785 a.m.u. and m n =.8665 a.m.u. and mass of helium nucleus is 4.8 a.m.u., then binding energy per nucleon of helium is () 7 MeV/nucleon () 5.6 MeV/nucleon 4.5 MeV/nucleon (4) 6. MeV/nucleon 53. The binding energies per nucleon for deutron ( H ) and helium ( He 4 ) are. MeV and 7. MeV, respectively. When two deutrons fuse to form a helium nucleus, the energy released is () 9.6 MeV () 3.6 MeV 6. MeV (4) 8. MeV 54. The frequency of revolution of an electron in nth circular ohr orbit of an atom, having atomic number Z is proportional to () Z 3 /n () Z /n 3 n /Z 3 (4) n 3 /Z 55. The speed of an electron, in nth circular ohr orbit of an atom of atomic number Z, is (c is velocity of light) () Z c 37 n Z c n () (4) Z c 37 n n c 37 Z 56. In Rutherford s -scattering experiment, the ratio of number of -particles scattered through an angles of 6º and º is () : () 3 : 3 : (4) 9 : 57. Time taken by the electron to complete first orbit of hydrogen atom is () s () s.5 6 s (4) s 58. What is the angular momentum associated with electron of hydrogen atom, when its energy is 3.4 ev? (h = Js) (). 34 Js () Js Js (4) none of these 59. What is the potential energy of proton at the nucleus of hydrogen atom when the electron is in the second orbit of the hydrogen atom? () 3.4 ev () 6.8 ev. ev (4) 3.6 ev 6. The atomic mass of 7 N 5 is 5.8 a.m.u. and that of 8 O 6 is a.m.u. If the mass of proton is.785 a.m.u., then the minimum energy provided to remove the least tightly bound proton is ().38 MeV (). MeV 3.8 MeV (4). ev 6. The wavelength of first member of almer series in hydrogen spectrum is. The wavelength of first member of Lyman series in the same spectrum is () (5/7) () (4/7) (7/5) (4) (7/4) 6. If wavelength of the energy emitted when electron comes from fourth orbit to second orbit in hydrogen is,397 units, then the wavelength of energy for the same transition in He + is () 5,99 units (),497 units 4,494 units (4) 8,988 units 63. Energy levels,, C of a certain atom correspond to increasing values of energy i.e. E < E < E C. If, and 3 be the wavelengths corresponding to the transitions C to, to and C to respectively, which of the following is correct? () = 3 3 () 3 = 3 = + (4) 3 = The wavelength of K line for an element of atomic number 43 is. Then the wavelength of K line for an element of atomic number 9 is about () 43/9 () 4/8 9/4 (4) 43 / particle of 6 MeV is incident head-on against the nucleus of gold of atomic number 79. The distance of nearest approach of -particle with respect to the nucleus of gold is nearly () 38 fermi () 58 fermi 3.8 fermi (4) 5.8 fermi [8]

13 tomic & Nuclear Physics 66. With usual meanings of the symbols, impact parameter (b) is given by the relation () () (4) b 4 b 4 b 4 b 4 Z e cot ( /). E Z. Z. Z e. e cot ( /) E e cot ( /) E cot ( /) E 67. ssuming that in a star, three -particles join in a single fusion reaction to form a 6 C nucleus, calculate the energy released in this reaction. Given : mass of He 4 = 4.64 a.m.u. and mass of 6C =. a.m.u. () MeV ().4 MeV 5.4 MeV (4) 7.3 MeV 68. The maximum wavelength of almer series for H-atom is () 6653 Å () 6563 Å 7366 Å (4) 5766 Å 69. Frequency of the series limit of almer series of hydrogen atom in terms of Rydberg constant R and velocity of light C is () c R () c R/4 4 c R (4) 4/c R 7. One state of the triply ionized berilium has the same orbital radius as that of ground state of hydrogen. Find the ratio of energies of the electrons of the atoms in these two states () 4 : () 6 : 8 : (4) : 7. One level of the doubly ionized lithium has same energy as the ground state energy of the hydrogen atom. The ratio of orbital radii of these two energy levels is () : () 3 : 9 : (4) : 7. single electron orbits a stationary nucleus of charge +Ze, where Z is a constant and e is the magnitude of electronic charge. It requires 4.8 ev to excite the electron from the second to the fourth ohr orbit. The value of Z is () 3 () 4 5 (4) n electron of stationary hydrogen atom passes from fifth to ground state. What energy will the atom release as a result of photon emission? ().88 ev () 3.56 ev.75 ev (4) 3.65 ev 74. In hydrogen atom, radiation emitted due to transition of electron from third orbit to second orbit is. For a singly ionized helium atom to emit the radiation of same wavelength, electron transition should be () n = 3 to n = () n = to n = n = 5 to n = 3 (4) n = 6 to n = If curie = 3.7 disintegration/sec., find the mass of one curie of uranium-34. () 3.7 g () 3.88 g.94 g (4).438 g 76. In a thermonuclear reactor, 3 kg of hydrogen is converted into kg of helium. If efficiency of the reactor is 5%, the energy produced by it in the form of electrical energy is () 9.93 MWh () 8.75 MWh 95 MWh (4) 9.45 MWh 77. Hydrogen atom in its ground state is excited by means of a monochromatic radiation of wavelength 97.6Å. How many different wavelengths are possible in the resulting emission spectrum? (h = Js) () 6 () 3 (4) In a radioactive decay, let N be the number of residual active nuclei, D the number of daughter nuclei, T / half life and M the mass of active sample at any time t. elow are shown four curves. (i) N (iii) T / t (ii) t t The correct curves are () (i), (ii) and (iv) () (ii), (iii) and (iv) (i), (ii) and (iii) (4) all of these D (iv) M 79. In a given sample, half lives of two radioactive substances and are, respectively, 4 hr and hr. fter a time of hours, percentage of mass of given sample left is () 5 % ().5 % 6 / 3 % (4) 6.5 % t [9]

14 tomic & Nuclear Physics 8. Two radioactive materials X and X have decay constants and respectively. If initially they have the same number of nuclei then the ratio of the number of nuclei of X to that of X will be /e after a time () /() () /() /() (4) /(9) 8. radioactive sample, with half-life = T, emits -particles. Its total activity is i at some time and f at a later time. The number of -particles emitted by the sample between these two points in time is T () i f () i f n n T i f (4) T n f i 8. The count rate from cm 3 of a radioactive liquid is c. Some of this liquid is now discarded. The count rate of the remaining liquid is found to be c/ after three half-lives. The volume of the remaining liquid, in cm 3, is () () 4 6 (4) What percentage of radioactive substance is decayed in 5 half-lives? () 97.75% () % 96.75% (4) almost % 84. radioactive sample at any instant has its disintegration rate 5 disintegration per minute. fter 5 minutes, the rate is 5 disintegrations per minute. Then the decay constant (per minute) is ().693 () (4) t an instant, the ratio of the amounts of radioactive substances is :. If their half-lives be, respectively, hrs and 6 hrs, then after 4 days the ratio of the amounts of substances left over will be () : () : : (4) : Initially masses of radioactive substances and are equal. Their half-lives are respectively hour and hours. fter hours, their activities would be in the ratio () : () : : (4) : If % of a radioactive material decays in 5 days, then the amount of the original material left after days is approximately () 6% () 65% 7% (4) 75% 88. In a sample of radioactive material, what percentage of the initial number of active nuclei will decay during one mean life? () 37 % () 5 % 63 % (4) 7 % 89. Three-fourths of the active nuclei present in a radioactive sample decay in 3 / 4 s. The half-life of the samples is () s () / s 3 / 4 s (4) 3 / 8 s 9. sample of radioactive material has mass m, decay constant, and molecular weight M. vogadro constant = N. The initial activity of the sample is m () m () M m N (4) mn e M 9. In the previous question, the activity of the sample after time t will be () mn M e mn e M t t () mn t m M e t (4) e 9. small volume of a solution which contained a radioactive isotope of sodium had an activity of, disintegrations per minute when it was injected into the blood stream of a patient. fter 3 hours, the activity of. cm 3 of the blood was found to be.5 disintegrations per minute. If the half life of the sodium isotope is taken as 5 hours, estimate the volume of blood in the patient. () cm 3 () 3 cm 3 4 cm 3 (4) 6 cm The radioactivity of a sample is R at a time T and R at a time T. If the half life of the specimen is T, the number of atoms that have disintegrated in the time (T T ) is proportional to () (R T R T ) () (R R ) (R R ) /T (4) (R R ) T 94. K 4 isotope of potassium has a half life of.37 9 years and decays to an isotope of argon which is stable. In a particular sample of moon rock, the ratio of potassium atom to argon atoms was found to be : 7. Estimate the age of the rock, assuming that originally there was no argon present. () 4. 9 years ().74 9 years years (4).37 9 years []

15 tomic & Nuclear Physics 95. The sample of a radioactive substance has 6 nuclei. Its half life is s. The number of nuclei that will be left after s is nearly () 5 () (4) The intensity of gamma radiation from a given source is I. On passing through 37.5 mm of lead it is reduced to I /8. The thickness of lead which will reduce it to I / is () (37.5) /3 mm () (37.5) /4 mm (37.5/3) mm (4) (37.5/4) mm 97. The first ohr radius of a mesonic hydrogen atom (i.e., an atom in which a negative muon of mass 7 m e orbits around a proton instead of an electron) is nearly ().5 3 m (). m.53 m (4) 7. m 98. n energy of 4.6 ev is required to remove one of the electrons from a neutral helium atom. The energy in (ev) required to remove both the electrons from a neutral helium atom is () 38. () (4) Imagine an atom made up of a proton and a hypothetical particle of double the mass of the electron but having the same charge as the electron. pply the ohr atom model and consider all possible transitions of this hypothetical particle to the first excited level. The longest-wavelength photon that will be emitted has wavelength (given in terms of the Rydberg constant R for the hydrogen atom) equal to () 9/(5R) () 36/(5R) 8/(5R) (4) 4/R. radioactive source, in the form of a metallic sphere of radius cm, emits -particles at the rate of 5 particles per second. The source is electrically insulated. How long will it take for its potential to be raised by V, if 4% of the emitted -particles escape the source? () 6.9 ms () s 9.6 ms (4).3 ms []

16 Solids, Semiconductor Devices & Communication Choose the correct answers :. Space between atoms in crystals is of the order of wavelength of () infra-red rays () ultraviolet rays X-rays (4) -rays. solid which is opaque to visible light and whose electrical conductivity decreases with increasing temperature is characterised by () ionic binding () covalent binding metallic binding (4) van der Waal s binding 3. The atomic packing fraction for a face-centred cubic cell is () () /6 3 /8 (4) / 6 4. If is the atomic mass number of an element, N vogadro s number, a the lattice parameter of the cubic cell, then the density of an element with body centred cubic cell is () 3 Na 3 3 Na () 3 Na 4 (4) 3 Na 5. The denisty of an fcc lattice crystal is (N is vogadro number and is atomic mass and r is atomic radius of the element) 3 3 () 3 Nr 6 () 3 Nr Nr 8 (4) 3 Nr 6 6. The number of valance electrons in an atom of a good conductor is generally () four () three or less than three five (4) six or more than six 7. If lattice parameter is 3. Å in a FCC crystal, then the atomic radius of this crystal is ().6 Å ().386 Å.6 Å (4).3 Å 8. Which one of the following is wrong for hexagonal unit cell? () Co-ordination number is () Volume of unit cell is 3 a tomic packing factor is.74 (4) a = b c and c /a = 3/ 9. The bond length for FCC lattice (where a is lattice parameter) () a ().5 a.866 a (4).77 a. solid reflects light in the visible region, its resistivity decreases with temperature and its melting point is above ºC. Nature of binding in the solid is () ionic () covalent metallic (4) Van der Waals. The distance between the body centered atom and a corner atom in sodium (a = 4.5 Å) is () 3.66 Å () 3.7 Å.99 Å (4).54 Å. semiconductor has () equal amounts of negative and positive charges () no minority charge carriers no majority charge carriers (4) no free charges 3. In a unit cell, co-ordination number is, atomic packing factor is.74 and lattice vector, a = r (r = radius of atom). The unit cell is () simple cubic () body centred cubic face-centred cubic (4) hexagonal 4. If the mobility of electrons is 3.5 m V s, the mobility of holes is 4.8 m V s and the number of electron-hole pairs per unit volume is.7 6 m 3 in pure silicon crystal at 3 K, then its conductivity is () Sm () Sm Sm (4) Sm 5. Ge specimen is doped with l. The concentration of acceptor atoms is ~ atoms/m 3. Given that the instrinsic concentration of electron hole pairs is ~ 9 m 3, then the concentration of electrons in the specimen is () 7 m 3 () 5 m 3 8 m 3 (4) m 3 []

17 Solids, Semiconductor Devices & Communication 6. The depletion layer in a p-n junction diode consists of () positively charged donors on the p-side and negatively charged acceptors on the n-side () negatively charged donors on the p-side and positively charged acceptors on the n-side positively charged donors on the n-side and negatively charged acceptors on the p-side (4) negatively charged donors on the n-side and positively charged acceptors on the p-side 7. The depletion layer in a p-n junction contains charges which are () mostly majority carriers () mostly minority carriers mostly donor and acceptor ions (4) fixed donor and acceptor ions 8. When a p-n junction diode is forward-biased, the flow of current across the junction is mainly due to () the nature of the material () both drift and diffusion of charges only drift of charges (4) only diffusion of charges 9. p-n junction can be used as () rectifier () amplifier transistor (4) oscillator. silicon specimen is made into a p-type semiconductor by doping, on an average, one indium atom per 5 7 silicon atoms. If the number density of atoms in the silicon specimen is 5 8 atoms/m 3, then the number of acceptor atoms in silicon per cubic centimetre will be ().5 atoms/cm 3 ().5 8 atoms /cm 3. 3 atoms/cm 3 (4). 5 atoms/cm 3. The ratio of electron and hole currents in a semiconductor is 7 : 4 and the ratio of drift velocities of electrons and holes is 5 : 4. Then, the ratio of concentrations of electrons and holes in the semiconductor is () 5 : 7 () 7 : 5 35 : 4 (4) 5 : 49. Doping is a process of () purifying the material () adding controlled impurities in the material making the material crystalline (4) making the material amorphous 3. The electrical conductivity of a semi-conductor increases when electromagnetic radiation of wavelength shorter than 48 nm is incident on it. The band gap for the semi-conductor is about ().9 ev ().7 ev.5 ev (4). ev 4. The dominant mechanisms for motion of charge carriers in forward and reverse biased silicon p-n junctions are () drift in forward bias, diffusion in reverse bias () diffusion in forward bias, drift in reverse bias diffusion in forward as well as in reverse bias (4) drift in forward as well as in reverse bias 5. The avalanche breakdown in p-n junction is due to () shift of Fermi level () cummulative effect of conduction-band-electon collision widening of forbidden gap (4) high impurity concentration 6. When the reverse bias in a junction diode is changed from 5 V to 5 V the value of current changes from 38 to 88. The resistance of the junction diode would be () 4 5 () (4) 6 7. In thermionic emission, the thermionic current density varies with temperature of the filament as () T () T T (4) /T 8. semiconductor has electron concentration and hole concentration as n e and n p, respectively. If electron mobility and hole mobility are, respectively, e and p of the given sample, then the resistivity of the semiconductor is equal to () e(n e e + n p p ) () e( n e n ) n e e n e p p (4) e e n e n 9. The depletion layer in p-n junction is caused by () drift of holes () drift of electrons diffusion of charge carriers (4) migration of impurity ions e p p p p [3]