WORKSHEET. 1. How does the Coulomb force between two point charges depend dielectric constant of the intervening medium?

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1 WORKSHEET 1. How does the Coulomb force between two point charges depend dielectric constant of the intervening medium? 2. Define the term electric field intensity. Electric field inside a conductor is zero explain. 3. Force of attraction between two point charges placed distance d apart in a medium is F. What would be the distance in the same medium so that the force of medium attraction between them becomes F/4? 4. A sphere s 1 of radius r 1 encloses a total charge Q. If there is another concentric sphere s 2 of radius r 2 (>r 1 ) & there is no additional charge between s 1 and s 2 find the ratio of electric flux through s 1 and s How does electric field strength changes with distance r for a short electric dipole? 6. What is the direction of the torque acting on a dipole placed in a uniform electric field? 7. A charge q is placed at one of the corner of a cube of side a. What is the electric flux associated with the cube? 8. No two electric field lines forces intersect. why? 9. Which orientation of an electric dipole in a uniform electric field would correspond to stable equilibrium? 10. Draw a plot showing the variation of electric field with distance r due to a point charge Q. 1 [XII Physics]

2 1. The electrostatic force on a small sphere of charge 0.4 µc due to another small sphere of charge 0.8 µc in air is 0.2N (a) What is the distance between the two spheres? (b) What is the force on the second due to the first. 2. A conducting sphere of radius 10 cm has an unknown charge. If the electric field 20 cm from the centre of the sphere is N/C and points radially in words what is the net charge on the sphere? 3. A charge q is placed at the mid point of the line joining two equal charges Q. Show that the system of three charges will be an equilibrium if q = Q/4. 4. The sum of two point charges is 9 µc. They repel each other with a force of 2N when kept 30 cm apart in free space. Calculate the value of each charge. 5. Two point charges q and 4q are separated by 1m in air. At what point on the line joining the charges is the electric field intensity zero? 6. Derive an expression for the electric field at any point on the axial line of a short electric dipole. 7. A cubical Gaussian surface encloses a charge of C (in vacuum) at centre. Calculate the electric flux through the one of its faces. 8. State Gauss s Law in electrostatics. Using this Law derive an expression for the electric field due to a uniformly charged infinite plane sheet. 9. An electric dipole when held at 30 with respect to a uniform electric field of 10 4 N/C experience a torque of Nm calculate the dipole moment of the dipole. 10. If the radius of the spherical Gaussian surface enclosing a charge is halved, how does the electric flux through the Gaussian surface change? [XII Physics] 2

3 WORKSHEET 1. Name the physical quantity which has its unit JC 1. Is it a scalar or vector quantity. 2. Name the physical quantity whose SI unit is (i) Ampere/volt (ii) Newton/Coulomb 3. Write down the relation between the electric field and electric potential at a point. 4. What is the work done in moving a charge of 10 µc between two points on an equipotential surface? 5. What is the amount of work done in moving a 100 µc charge on the circumference of circle when charge q is placed at centre. 6. A and B are two conducting spheres of same radii. A being solid and B is hollow. Both are charged to the same potential. What will be the relation between the charge on the two sphere. 7. Draw equipotential surface of uniform electric field? 8. Why does the electric field inside a dielectric decreases when it is placed in an external electric field? 9. Why are capacitors joined in (i) series, (ii) parallel? 10. A capacitor C is charged to a potential V. What is the electric flux of the electric field passing through a closed surface around the capacitor? 3 [XII Physics]

4 1. Two tiny sphere carrying charges 1.5 µc and 2.5 µc are located 30 cm apart. Find the potential and electric field. (a) at the mid point of the line joining the two charges. (b) at a point 10 cm from the mid point towards 2.5 µc. 2. Derive an expression for the energy stored in a parallel plate capacitor with air as the medium between its plates. 3. Define the term electrostatic potential. Give the expression of electrostatic potential due to a small electric dipole at a point lying on : (i) the axial line and (ii) equitorial line. 4. What is the area of the plates of a 2 µf parallel plate capacitor, given that the separation between the plates is 0.5 cm? 5. Two charges C and C are located 16 cm apart. At what point on the line joining the two charges is the electric potential zero? Take the potential at infinity to be zero? 6. A 600 pf capacitor is charged by a 200 V supply. It is then disconnected from the supply and is connected to another uncharged 600 pf capacitor. How much electrostatic energy is lost in the process? 7. A parallel plate capacitor with air between the plates has a capacitance of 8 pf- what will be the capacitance if the distance between the plates is reduced by half and the space between them is filled with the substance of diaelectric constant 4? 8. In a parallel plate capacitor with air between the plates, each plate has an area of cm 2 and distance between the plates is 3mm. Calculate the capacitance of the capacitor. If this capacitor is connected to a 100V supply what is the charge on the capacitor? [XII Physics] 4

5 WORKSHEET 1. State the condition in which terminal voltage across a secondary cell is equal to its emf. 2. What is the order of magnitude of drift velocity in conductor? 3. Two wires A and B are of same metal, have the same area of cross section and have their length in the ratio 2:1 what will be the ratio of currents flowing through them, when the same potential difference is applied across length of each of them, 4. What is the effect of increase in temperature on : (i) Relaxation time of electrons in metals; (ii) The drift velocity 5. V-I graph for a given metallic wire at two temp are shown which of these is for a higher temperature. I T (1) T (2) 6. Two wires of equal length one of copper and the other of aluminium have the same resistance which wire is thicker? 7. Metal or alloy which of them has greater value of temperature coefficient of resistance? 8. Sketch a graph showing variation of resistivity of carbon with temperature. 5 [XII Physics]

6 9. The sequence of marked on a carbon resistor are yellow, red, orange and silver write the value of resistance with tolerance? 10. What happens to the power dissipation if the value of electric current passing through a conductor of constant resistance is doubled? 11. Two heater wires of the same dimensions are first connected in series and then in parallel to a source of supply. What will be the ratio of heat produced in two cases? 12. Why are connecting wires in a metre bridge made of thick copper strips? 1. Determine the current in each branch of the network V 2. A storage battery of emf 8V and internal resistance 0.5 is being charged by a 120v DC supply using a series resistor of 15.5 what is the terminal voltage of the battery during charging? What is the purpose of having a series resistor in the charging circuit? 3. A cylindrical metallic wire is stretched to increase its length by 5% calculate the percentage change in its resistance? 4. Calculate the equivalent resistance of the resistance network between the points A and B as shown in figure when switchs is closed? 8 12 s 12 8 [XII Physics] 6

7 5. Calculate the resistance between A and B of the given network shown in figure. 2 A B 6. AB is a 1m long uniform wire of 10 resistance, the other data are shown in the circuit diagram calculate. 2 (i) (ii) Potential gradient along AB Length AO of the wire when galvanometer shows no deflection. E = 2V 15 A 1.2 E = 1.5V O G B How can a given 4 wires potentiometer be made more sensitive? 8. 5 Identical cells each of emf E and internal resistance r are connected in series to form a closed circuit. If an ideal voltmeter is connected across 3 cells what will be its reading? 9. A resistor of 24 is bent in the form of a loop as shown in Figure. Calculate the effective resistance between Points A & B. A B 10. What is Wheatstone bridge? Deduce the condition for which wheatstone bridge is balanced? 7 [XII Physics]

8 WORKSHEET 1. Under what condition does an electron moving through a magnetic field experience maximum force? 2. How will the magnetic field intensity at the centre of a circular coil carrying current change if the current through the coil is doubled and the radius of the coil is halved? 3. When a charged particle enters a magnetic field at right angles to the field which one of the following does not change. (i) velocity of the particle; (ii) momentum of particle (iii) energy of the particle. 4. An electron beam is moving vertically upward if it passes through a magnetic field which is directed from south to north in a horizontal place, then in which direction will be beam be deflected? 5. A current carrying wire is placed in a magnetic field. In which situation the force experienced by the conductor is maximum and minimum. 6. An electron and a proton moving parallel to each other in the same direction with equal momentum enter into a uniform magnetic field which is at right angles to their velocities. Trace their trajectories in the magnetic field. 7. Which one of the following will experience maximum force when projected with the same velocity and perpendicular to the magnetic field (i) particle (ii) particle. 8. What is the advantage of using radical magnetic field in a moving coil galvanometer. [XII Physics] 8

9 9. What is shunt? State its uses. Find the relation for the current through shunt in terms of resistance of galvanometer and shunt? 10. Which one of the two an ammeter or a milli ammeter has a high or resistance and why? 1. A long straight wire carries a current of 35A what is the magnitude of the field B at a point 20cm from the wire. 2. What is the magnitude of magnetic force per unit length on a wire carrying a current of 8A and making an angle of 30 with the direction of a uniform magnetic field of 0.15T? 3. A galvanometer coil has resistance 12 and the meter shows full scale deflection for a current of 3mA. How will you convert the meter into an ammeter of range 0 to 6A? 4. Two long and parallel straight wire A and B carrying current of 8.0 A and 5.0 A in the same direction are separated by a distance of 4.0 cm. Estimate the force on a 10cm section of wire A. 5. A galvanometer coil has resistance 12 and the meter shows full scale deflection for a current of 3mA. How will you convert the galvanometer into a voltmeter of range 0 18V. 6. A closely wound solenoid 80cm long has 5 layers of winding of 400 turns each. The diameter of the solenoid is 1.8 cm if the current carried is 8.0A Estimate the magnitude of B inside the solenoid near its centre? 7. Derive expression for magnetic field due to a straight conductor carrying current at a point (i) r > R (ii) r < R. R radius of cross section. 8. Derive an expression for magnetic field due to current flowing in a toroid. 9. What is a cyclotron? Discuss its construction and working. Explain cyclotron frequency. 10. What is an ammeter? How can a galvanometer be converted into an ammeter? Explain. 9 [XII Physics]

10 WORKSHEET 1. How does the (i) pole strength (ii) magnetic moment of each part of a bar magnet change if it is cut into two equal pieces along its length? 2. Why do magnetic field lines prefer to pass through iron than through air? 3. What are the value of (i) The horizontal component of earth s magnetic field and (ii) angle of dip at the magnetic north pole of the earth? 4. What is the angle of dip at a place, where the horizontal component and vertical component of the earth magnetic field are equal? 5. Horizontal component of earth s magnetic field at a place is 3 times the vertical component. What is the value of angle of dip at this place? 6. Why should the material used for making permanent magnets have high coercivity? 7. What type of magnetic material is used in making electro magnets. 8. State the reason why soft iron is used in making electromagnet. 9. If the ratio of the horizontal components of earth magnetic field to the resultant magnetic field at a place is 1/ 2. What is the angle of dip at that place. 10. How does the intensity of magnetization of a paramagnetic sample vary with temperature? 1. A circular coil of N turns and radius R carries a current I. It is unwound and rewound to make another coil of radius R/2 current I remaining the [XII Physics] 10

11 same. Calculate the ratio of the magnetic moments of the new coil and the original coil. 2. Deduce the expression for the magnetic dipole moment of an electron orbiting around the nucleus. 3. The horizontal component of earth s magnetic field at a place is B and the angle of dip is 60. What is the value of vertical component of earth s magnetic field at equator. 4. The permeability of a magnetic material is Name the type of magnetic material it represent. 5. The susceptibility of a magnetic material is Name the type of magnetic material it represent. 6. A magnetic needle free to rotate in a vertical plane parallel to the magnetic meridian has it north tip down at 60 with the horizontal. The horizontal component of the earth magnetic field at the place is known to be 0.4 G. Determine the magnitude of the earth s magnetic field at the place. 7. Derive an expression for the torque experienced by a magnetic dipole in a uniform magnetic field. 8. Show that how does a current loop act as a magnetic dipole. Derive an expression for its magnetic moment. 9. A circular coil of 50 turns and radius 20cm carries a current of 12A. Find magnetic moment associated with it. 10. A magnetized needle of magnetic moment J/T is placed at 30 with the direction of uniform magnetic field. The torque acting on the needle is J, calculate the magnitude of magnetic field? 11 [XII Physics]

12 WORKSHEET 1. A wire which is in N-S direction is dropped freely. Will any potential difference be induced across its ends? 2. Does Lenz s law violate the Principle of Conservation of Energy. 3. A glass rod of length l moves with velocity vi in an uniform magnetic field Bk. What is the emf induced in the rod. 4. Name various methods of producing induced emf. 5. Write expression of maximum emf for ac generator. 6. The magnitude of electric current is increasing from A towards B. If there is an induced current in the loop what will be its direction? A B 7. A coil is removed from a magnetic field (i) rapidly (ii) slowly. In which case more work will be done. 8. As soon as current is switched on a high voltage line the bird sitting on it flies away. Why? 9. A coil B is connected to a low voltage bulb L and placed parallel to another coil A explain the following observation (see figure). (i) Bulb lights [XII Physics] 12

13 (ii) Bulb gets dimmer if coil B is moved upwards. L B Ac A 10. Graph of magnetic flux and current I is shown for two inductor. A and B which of the two has Larger Value of self inductance? A B 11. How does the mutual inductance of a pair of coil change when I (i) (ii) distance between the coils is increased. number of turns in the coil is increased. 12. Predict the polarity of the capacitor in the situation described by Fig. Explain its reason. S N A B S N 1. A wheal with 10 metallic spokes each 0.5m long i.e. rotated with speed of 120 rpm, in the plane normal to earth s magnetic field at the place. If the magnitude of the field is 0.40 gauss, what is the induce emf between the axis and rim of the wheel. 13 [XII Physics]

14 2. A small piece of metal wire is dragged across the gap between the pole pieces of a magnet in 0.5 s. The magnetic flux between the pole pieces is known to be wb. Estimate the emf induced in the wire. 3. An emf of 0.5 V is developed in the secondary coil. When current in the primary coil changes from 5.0A to 2.0A in 200 milli second. Calculate the mutual inductance of the two coils. 4. Current in a circuit falls steadily from 2.0A to 0.0A in 10 milli second. If an average emf of 200V is induced. Calculate the self inductance of the circuit. 5. A source of emf E is used to establish a current I through a coil of self inductance L. Show that the work done by the source to build up the current I is ½LI What are eddy currents? How are these minimised? Mention two applications of eddy currents. 7. If a 10m long metallic bar moves in a direction of right angle to the magnetic field with a speed of 5.0 m/s, 25V emf is induced in it. Find the value of magnetic field intensity. 8. A railway track running N-S has two parallel rails 1.0m apart. Calculate the value of induced emf between the rails, when a train passes at a speed of 90 km/hr horizontal component of earth s field at that place is wbm 2 and angle of dip is The self inductance of an inductance coil having 100 turns is 20 mh. Calculate the magnetic flux through the cross section of the coil corresponding to a current of 4 ma. Also find the total flux. 10. If self inductance of an air core solenoid increases from 0.04 mh to 16 mh on introducing an iron core into it what is relative magnetic permeability of the core? [XII Physics] 14

15 WORKSHEET 1. How will inductive reactance and capacitive reactance change on doubling the frequency of alternating current? 2. What is the natural frequency of LC circuit? What is the reactance of this circuit at this frequency? 3. What is meant by Wattless current? 4. How can you improve the quality factor of a series resonance circuit? 5. In a pure LC circuit what is the energy stored when peak current is I 0? 6. At very high frequency of an a.c. a capacitor behaves as a good conductor. Why? 7. Can we use a capacitor instead of choke coil for reducing a.c.? 8. Which of the following quantities remain constant in a step down transformer? (a) current (b) voltage (c) power 9. Sketch a graph to show how the reactance of (i) a capacitor and (ii) an inductor varies as a function of frequency? 10. An ordinary moving coil ammeter used for d.c. cannot be used to measure an alternating current even if its frequency is low explain. 11. A capacitor blocks d.c. and allow a.c. Why? 15 [XII Physics]

16 12. At an airport a person is made to walk through the doorway of a metal detector for security reasons. If he/she is carrying anything made of metal the metal detector emits a sound, on what principle does this detector works? 1. Find the maximum value of current when inductance of two henry is connected to 150 volts, 50 Hz supply. 2. The instantaneous current from an a.c. sources is given by I=5 sin 314t what is emf value of the current? 3. Why is the iron core of a transformer made laminated? 4. How much current is drawn by the Primary coil of a transformer which steps down 220 volts to operate a device with an impedance of 220 ohm? 5. A 100 mh inductor, a 25 µf capacitor and 15 resistance are connected in series to a 120V, 50 Hz ac source. Calculate (i) (ii) (iii) Impedance of circuit at resonance Current at resonance Resonant frequency 6. A capacitor, a resistor and 40mH inductor are connected in series to an ac source of frequency 60Hz. Calculate the capacitance of the capacitor, if current is in phase with the voltage. 7. A bulb of resistance 10 connected to an inductor of Inductance L in series with an ac source 100V, 50 Hz, if the phase angle between voltage and current is /4 radian, calculate the value of L. 8. An AC voltage of 100V 20Hz is connected across a 20 resistor and 2mH inductor in series calculate (i) impedance of the circuit. (ii) rms current in the circuit. 9. Derive an expression for the average power consumed in a series LCR circuit connected to AC source for which the phase difference between the voltage and the current in the circuit is [XII Physics] 16

17 10. An AC source of emf E=Eosin t is connected across a series combination of L, C, and R obtain an expression for the equivalent impedance Z and hence find the value of for AC source for which Z = R. 17 [XII Physics]

18 WORKSHEET 1. What oscillates in an electromagnetic wave? 2. Which has higher wavelength rays, x rays and microwaves? 3. Why are microwaves used in Radar? 4. For which frequency of light the eye is most sensitive? 5. Name the electromagnetic radiations used for viewing the objects through haze and fog? 6. What is the limit of frequency up to which signals using sky waves can be transmitted? 7. Which physical quantity if any has the same value for waves belonging to the different parts of the electromagnetic spectrum? 8. Name the electromagnetic radiation to which the following wavelengths belong (a) 10 2 m (b) 1A 9. A variable frequency a.c. source is connected to a capacitor. Will the displacement current increase or decrease with increase in frequency? 10. Why did Maxwell introduce the concept of displacement current? Explain. 11. Is it necessary to use satellite for long distance TV transmission? Give reason. 12. Explain that microwaves are better carriers of signals than radio waves. 13. What is the phase difference between electric and magnetic field vectors in an electromagnetic wave. [XII Physics] 18

19 14. Name the phenomenon which justifies the transverse nature of e.m. waves. 15. What modification was made by Maxwell in Ampere circuital Law? 1. A radio can tune into any station in the range 7.5 MHz to 12MHz band. What is the corresponding wavelength band? 2. Find the wavelength of electromagnetic waves of frequency Hz in free space. Give its two application. 3. How would you establish an instantaneous displacement current of 1.0A in the space between the parallel plates of 1 µf capacitor. 4. In an electric circuit there is a capacitor of reactance 100 connected across the source of 220V find the displacement current. 5. In a plane electromagnetic wave the electric field oscillates sinusoidally at a frequency Hz and Amplitude 50 V/m. (a) (b) What is the wavelength of the wave? What is the amplitude of the oscillating magnetic field? 6. The magnetic field in a plane electromagnetic wave is given by = sin [ x t] tesla. (a) (b) What is the wavelength & frequency of the wave? Write an expression for the electric field? 7. A beam of light travelling along x axis is described by the magnetic field By = sin (t x/c) tesla. Calculate the maximum electric and magnetic forces on an charged of a electron moving along y axis with a speed of m/s charge on electron = C. 8. An em wave travelling through a medium has electric field vector E y = cos ( t 1.5x) N/c here x is in metre and t is in second. Find 19 [XII Physics]

20 (i) (ii) (iii) (iv) (v) wave length speed of wave frequency direction of propagation amplitude of magnetic field vector. [XII Physics] 20

21 WORKSHEET 1. A concave mirror is held in water. What would be the change in the focal length of the mirror? 2. For the same angle of incidence the angle of refraction in medium A, B and C are 35, 25, 15 respectively. In which medium will the velocity of light be minimum. 3. Why does the rising sun appear bigger? 4. An equiconvex laws of focal length 15 cm is cut into two equal halves in thickness. What is the focal length of each half? 5. What is the difference between the virtual image produced by (i) plane mirror (ii) concave mirror (iii) convex mirror? 6. A ray incident along normal to the mirror retraces its path why. 7. Can a virtual image be photographed? 8. A person moves with a velocity v towards a plane mirror with what velocity does his image move towards him? 9. Which of the following does not change when light goes from one medium to other. Frequency, wave length, speed, intensity? 10. A lens of glass is immersed in water. How is power of lens affected? 11. A lens when immersed in a transparent liquid becomes invisible. Under what condition does it happen? 12. Does critical angle depend on colour of light? 13. What is the cause of refraction of light? 14. How does focal length of a lense change when red light is replaced by blue light? 21 [XII Physics]

22 1. On what factor does the angle of minimum derivation produced by a prism depends? 2. On what factor does the dispersive power of a prism depend? 3. How does the amount of scatterings depend on the wavelength of light used? 4. For a simple microscope would you prefer a lens of higher focal length or smaller focal length? Why? 5. What happens to the magnifying power of a compound microscope when length of the microscope tube is increased? 6. How does magnifying power of a telescope change on decreasing the aperture of its objective lens? Justify your answer? 7. What is the distance between objective and eyepiece of an astronomical telescope in its normal adjustment? 8. The sun is seen a little before it rises and for a short while after it set explain why? 9. Give reason for the observation sun looks reddish at sunset. 10. Derive the relation between refractive index of a medium and its critical angle? 11. Explain briefly the formation of mirage in desert. 12. What is rainbow? How is it formed. Differentiate between a primary and secondary rainbow with the help of a diagram? 1. A convex lens of refractive index 1.5 has a focal length of 18 cm in air. Calculate the change in its focal length when it is immersed in water of refractive index 4/3. [XII Physics] 22

23 2. A ray of light incident on an equilateral glass prism (µg= 3) moves parallel to the base line of the Prism inside it. Find the angle of incident for this ray. 3. The radii of curvature of the faces of a double convex lens are 10 cm and 15 cm. If focal length of the lens is 12 cm find the refractive index of the material of the lens. 4. A biconvex lens has a focal length 2/3 times the radius of curvature of either surface calculate the refractive index of lens material. 5. Find the radius of curvature of the convex surface of a plane convex lens whose focal length is 0.3 m and the refractive index of the material of the lens is Calculate the distance of an object of height h from a concave mirror of focal length 10 cm. So as to obtain a real image of magnification A screen is placed 100 cm from an object. The image of the object on the screen is formed by a convex lens at two different locations separated by 20 cm calculate the focal length of the lens used. 8. A convex lens has 10 cm focal length in air what is its focal length in water? (Refractive index of air water = 1.33, air glass = 1.5). 9. An object of 3 cm height is placed at a distance of 60 cm from a convex mirror of focal length 30 cm. Find the nature, position and size of the image formed. 1. A convex lens of focal length 25 cm is placed coaxially in contact with a concave lens of focal length 20 cm. Determine the power of the combination, will the system be converging or diverging in nature? 2. Define the term resolving power of a telescope. How does it get affected on (i) increasing the aperture of the objective lens? 23 [XII Physics]

24 (ii) increasing the focal length of the objective lens? 3. An astronomical telescope uses two lenses of Power 10D and 1D. What is its magnifying power in Normal adjustment? 4. The focal length of the objective and eye piece of a microscope are 1.25cm and 5cm respectively. Find the position of the object relative to the objective in order to obtain an angular magnification of 30 in normal adjustment. 5. The near point of a hypermetropic person is 50cm from the eye. What is the power of the lens required to enable the person to read clearly a book held at 25cm from the eye? 6. Calculate the resolving power of a telescope assuming the diameter of the objective lens to be 6cm and the wavelength of light used to be 540 nm. 7. Draw a ray diagram for the formation of image by a compound microscope. Define its magnifying power. Deduce the expression for the magnification power of microscope. 8. Write three distinct advantages of a reflecting type telescope over a refracting type telescope. 9. You are given three lens of power 0.5D, 4D, 10D state with reason which two lenses will you select for constructing a good astronomical telescope? [XII Physics] 24

25 WORKSHEET 1. Can two independent (60W) bulbs be used to produce interference? 2. Find the ratio of intensities at two points on a screen in Young s double slit experiment, when waves from the two slits have path difference of (i) 0 (ii) /4 3. Two identical coherent waves each of intensity I are producing an interference pattern. Write the value of the resultant intensity at a point of (i) constructive interference and (ii) destructive interference. 4. How does the intensity of central maxima change, if the width at the slit is halved in a single slit diffraction experiment? 5. If the angle between the planes of the polariser and analyser is 60 by what factor does the intensity of transmitted light change when passing through the analyzer. 6. Explain Malus s Law? 7. Draw a graph showing the variation of intensity of polarised light transmitted by an analyser. 8. What is the value of refractive index of a medium of polarising angle 60? 9. Two polaroids are placed at 90 to each other and the transmitted intensity is zero. What happens when one more polaroid is placed between these two bisecting the angle between them. 10. What is the effect on interference fringes in Young s double slit experiment if one slit is covered? 25 [XII Physics]

26 11. What is the cause of diffraction? 12. Can white light be used to produce interference? 13. Which field vector electric or magnetic is used to represent the polarization of e.m. waves? 14. When light travels from a rarer to a denser medium the speed decreases. Does the reduction in speed imply a reduction in energy carried by the light waves? 1. What is polarizing angle of medium of refractive index 3? 2. State Huygen Principle using this Principle draw a diagram to show how a plane wave front incident at the interface of the two media get refracted when it propagates from a rarer to a denser medium. Hence verify Snell s Law of refraction. 3. How does the fringe width of interference fringes changes. When the whole apparatus of Young s experiment is kept in a liquid of refractive index 1.3? 4. In Young s double slit experiment the two slits 0.12 nm apart are illuminated by monocromatic light of wavelength 420 nm. The screen is 1.0 m away from the slits. (i) (ii) Find the distance of the second (a) bright fringe (b) dark fringe from the central maximum. How will the fringe pattern change if the screen is moved away from the slit. 5. In a single slit diffraction experiment, a slit of width d is illuminated by red light of wavelength 650 nm. for what value of d will (i) The first minimum fall is at an angle of diffraction of 30 (ii) The first maximum fall is at an angle of diffraction of 30? [XII Physics] 26

27 6. Two slit in Young s double slit experiment have width in the ratio 8:1 what is the radio of amplitude of light waves from them. 7. For a given medium the polarizing angle is 60 what will be the critical angle for this medium? 8. An unpolarized beam of light is incident on a group of four polaroids which are arranged in such a way that the characteristic direction of each polaroid makes an angle of 30 with that of the preceding one. What fraction of incident unpolarized light is transmitted? 27 [XII Physics]

28 WORKSHEET 1. Show graphically how the stopping potential for a given photosensitive surface varies with frequency of incident radiation? 2. A proton and an electron have same kinetic energy. Which one has greater de Broglic wavelength and why? 3. A nucleus undergoes B decay. How does its (a) mass number (b) atomic number change? 4. With what purpose was the famous Davisson - Germer experiment with electron performed? 5. It is easier to remove an electron from sodium than from copper? What metal has higher value of threshold frequency? 6. Does each incident photon essentially eject a photoelectron? 7. Blue light can eject electrons from a photosensitive surface while orange light cannot. Will violet and red light eject electrons from the same surface. 8. Show that de Broglic hypothesis of matter wave supports the Bohr s concept of stationary orbit. 9. Describe photoelectric effect and state the law of photoelectric emission. 10. Plot a graph showing the variation of photoelectric current with anode potential for two light beam of same wavelength but different intensity. 11. A particle of Mass M at rest decays into two particles of masses m 1 and m 2 having velocities v 1 and v 2 respectively. Find the ratio of de Broglic wavelengths of two particles. [XII Physics] 28

29 1. Calculate the frequency of a photon whose energy is 50ev. Given h = Js and e = C. 2. Calculate the maximum kinetic energy of electrons emitted from a photosensitive surface of electrons 3.2 ev, for the incident radiation of wavelength of 300nm given h = Js. 3. When light of wavelength 400nm is incident on the cathode of a photocell, the stopping potential recorded is 6v. If the wavelength of the incident light is increased to 600nm calculate the new stopping potential [Given h = Js, c = m/s, e = C] 4. Ultra violet light of wavelength 800A and 700A when allowed to fall on hydrogen atoms in their ground state is found to liberate electrons with KE 1.8ev and 4ev respectively. Find the value of Planck s constant. 5. The maximum KE of a photoelectron is 3ev. What is its stopping potential? 6. The stopping potential is an experiment on photoelectric effect is 2v. What is the maximum KE of the photoelectrons emitted? 7. An electron is accelerated through a potential difference of 64v what is the de Broglie wavelength associated with it? To which part of the electromagnetic spectrum does this value of wavelength correspond? 8. Find the ratio of the de Broglie wavelength associated with (i) Protons accelerated through a potential difference of 128V (ii) particles accelerated through a potential of 64V. 9. Derive an expression for the de Broglie wavelength associated with an electron accelerated through a potential v. Draw a schematic diagram of a localized wave describing the wave nature of the moving electron. 10. Write Einstein photoelectric equation and point and any two characteristic properties of photons on which this equation is based. 29 [XII Physics]

30 WORKSHEET 1. The ionization potential of hydrogen atom is 13.6eV. What will be its energy in n = 2 state? 2. Energy levels of an atom are shown below which one of the transitions will result in the emission a photon of a wavelength 275 nm? A B C D 0 ev 2 ev 4.5 ev 10 ev 3. The value of ground state energy of a Hydrogen atom is 13.6eV. What does the negative sign signify? 4. Name the series of Hydrogen spectrum which lies in the uv region. 5. An electron jumps from the fourth to the first orbit. How many spectral lines are possible? 6. How is the radius of the nucleus of an atom related to its mass number? 7. Write two limitations of Bohr s Atomic Model. 8. Using Bohr s postulate of atomic model derive mathematical expressions for kinetic & potential energy of an electron revolving in an orbit of radius r. 9. What is Bohr Radius? Derive an expression for the same. 10. Draw the energy level diagram for Hydrogen atom at room temperature. [XII Physics] 30

31 WORKSHEET 1. Two nuclei have mass in the ratio 8:125. What is the ratio of their nuclear radii? 2. Two nuclei have mass in the ratio 2:5. What is the ratio of their nuclear density? 3. A radioactive nucleus A undergoes a series of decay according to the following schemes A A A A A The mass and atomic number of A 4 are 172 and 69 respectively. What are these numbers for A? 4. Draw a graph between binding energy per nucleon and mass number. 5. Give reason for decrease in binding energy per nucleon for nuclei with higher mass number. 6. Why do lighter nuclei usually undergo nuclear fusion? 7. Half life of U against decay is s. What is the activity of a sample of U having atoms. 8. Draw a graph showing variation of potential energy of a pair of nucleons as a function of their separation. 9. Mass of a nucleus in its ground state is always less than the total mass of its constituents neutrons and protons : explain. 10. If the total mass of the neutrons and protons in a nuclear reaction is conserved, how then is the energy absorbed or evolved in the reaction? 31 [XII Physics]

32 WORKSHEET 1. What is the order of energy gap in a semiconductor? 2. What is the order of energy gap in conductor and insulators? 3. What is the conductivity of a semiconductor at absolute zero? 4. What is Fermi energy level? 5. Where does the Fermi level of an intrinsic semiconductor lie? 6. Why does diamond behave like an insulator? 7. How does the conductivity of a semiconductor change with the rise in its temperature? 8. Give the ratio of the number of holes and number of conduction electrons, in an intrinsic semiconductor. 9. Why doping is done in semiconductors? 10. Doping silicon with indium leads to which type of semiconductor. 11. Which type of charge carriers are there in a p-type semiconductor and n- tpe semiconductor? 12. What are donor impurity atoms? 13. The forbidden energy gaps in insulators, semiconductors and conductors are EG 1, EG 2 and EG 3 respectively. Arrange them in ascending order. 14. How does the energy gap of an intrinsic semiconductor vary, when doped with a trivalent impurity? [XII Physics] 32

33 15. Why is germanium preferred over silicon for making semiconductor devices? 16. Define mobility of charge carrier. Give its unit (SI). 17. Which has higher mobility - electron or hole? 18. Is Ohm s Law obeyed by semiconductor? 19. Draw the energy band diagram for intrinsic semiconductor. 20. How does the junction width change, when a p-n junction is form and - biased? 21. When does a p-n junction work as an open switch? 22. State the function of a Zener-diode in a circuit. 23. Can two p-n junction diodes placed back to back work as a pn-n-p transistor? 24. Can we interchange emitter and collector of a transistor? 25. A transistor is being used as a common emitter amplifier. What is the value of phase difference, if any, between the collective-emitter voltage and input signal? 26. Why is common emitter amplifier preferred over a common base amplifier? 27. When is a common base amplifier preferred over a common-emitter amplifier? 28. Under what condition a transistor works as an open circuit? 29. What is the direction of diffusion current in a junction diode? 30. What will be the frequency of oscillation of an oscillator with L and C as inductance and capacitance of its tank circuit? 31. What type of feedback is required in an oscillator? Give reason. 32. Give the logic symbol of NAND gate. 33 [XII Physics]

34 33. Give the logic symbol of NOR gate. 34. Write the truth table for NAND gate. 35. Why is a NOT gate known as an inverter? 36. Why does the width of depletion layer of a p-n-junction increase in reverse biasing? 37. Distinguish between intrinsic and extrinsic semiconductors. 38. Deduce an expression for conductivity of a p-type semiconductor. 39. In the following diagrams, indicate which of the diodes are forward biased and which are reverse biased? O +2V +5V (i) (ii) 10V 12V (iii) (iv) 5V 40. In the following circuits, if the input waveform is as shown in the figure, what will be the output waveform (i) across R in fig. (9) and (ii) across the diode in fig. (b). Assume that the diode is ideal. +5V +5V 5V 0 (a) R 5V 0 (b) R [XII Physics] 34

35 41. The output of an unregulated d.c. power supply is to be regulated. Name the device that can be used for this purpose and draw the relevant circuit diagram. 42. Distinguish between Led and photodiode. 43. In only one of the circuits given before the lamp L lights. Which circuit is it? Give reason for your answer. R L 6V R L 6V (a) (b) 44. Give the symbol, and the truth table of each of the two logic gates, obtained by using the two gate combination shown below. A B Y A B Y (a) (b) 45. Given below is the circuit symbol of a logic gate and two input waveforms A and B. (i) Name the logic gate and (ii) write its truth table, (iii) Also give output waveforms. A B Y A B (a) (b) 46. A 10V zener diode along with a series resistance is connected across a 40V supply. Calculate the minimum value of the resistance required, if the maximum zener current is 50mA. 35 [XII Physics]

36 R I V I R V 47. Determine the currents through the resistances of the circuits shown below : D D D D 2.0V 20 (a) D D 2.0V 20 (b) D D 2.0V 20 (c) 2.0V 20 (d) 48. Write the Boolean and truth table for the circuit consisting of NOR gate given below : A B A B Y 49. How can an intrinsic semiconductor be converted into a (i) p-type (ii) n- type extrinsic semiconductor. Explain with the help of energy band diagrams. [XII Physics] 36

37 50. Explain with the help of a diagram how (i) depletion layer and (ii) potential barrier is formed in a p-n junction diode. On what factors does the magnitude of potential barrier depends. 51. Give three important use of each (i) LED (ii) Photodiode. 52. Briefly describe construction & working of a typical p-n junction solar cell. Also draw its I-V characteristic. Mention its uses. 53. With the help of a labelled circuit diagram, explain the use of a junction diode as a full were rectifier. Draw input and output wareforms. 54. Sketch and explain I-V characteristic of Zener-diode. Also explain what causes Zener breakdown in Zener-diode. Mention any one use of it. 55. Draw the circuit diagram to study the input and output characteristics of an n-p-n transistor in common emitter configuration. Show these characteristic graphically. Explain how (i) input resistance (ii) output resistance and (iii) current amplification factor of the transistor are calculated by using these characteristics. 56. Explain the use of a transistor as a switch. 57. With the help of a labelled circuit diagram, explain the use of p-n-p transistor as a common-emitter amplifier. Discuss the phase relationship between input and output voltages. 58. What is an oscillator? Give its working principle. With the help of labelled circuit diagram, explain how a transistor can be used to produce selfsustained oscillations. 59. What is an OR gate? Give Boolean expression, logic symbol and truth table for an OR gate. Explain, with the help of a circuit diagram, how is this gate realised in practice. 37 [XII Physics]

38 WORKSHEET 1. What are three elements of communication? 2. Name two types of signals. 3. What is modulation? 4. Name the types of modulation in analog communication. 5. What type of modulation is required for radio broadcast? 6. Why is short wave band used for long distance radio broadcast? 7. Give an example of amplitude modulation. 8. Name two uses of optical transmission. 9. What is the full name of LED? 10. On which phenomenon is optical fibre based? 11. What is the full name of LASER? 12. What is meant by band width of information signal? 13. Why high frequency carrier waves are employed for long distance transmission? 14. Name the communication channel used in optical transmission. 15. What do you mean by modulated wave? [XII Physics] 38

39 Submitted by : 1. Pundrikaksh Principal Govt. Co. Ed. Sr. Secondary School, Sector 15, Rohini, Delhi S. Vijaylakshmy (I.D ) 3. Seema Kaushik (I.D ) 4. Pratima Saigal (I.D ) 39 [XII Physics]