Higher Physics. Particles and Waves

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1 Perth Academy Physics Department Higher Physics Particles and Waves Particles and Waves Homework Standard Model 1 Electric Fields and Potential Difference 2 Radioactivity 3 Fusion & Fission 4 The Photoelectric effect 5 Interference & Diffraction 6 Refraction and Total Internal Reflection 7 Light Irradiance 8 Emission Spectra 9 Absorption Spectra 10

2 Homework 1: Standard Model 1. (a) Write down the names of the 6 quarks and arrange them into their usual 3 pairs. (b) Label each quark with its electric charge in coulombs. (c) What is the quark content of a neutron and the quark content of a proton? (d) What happens to the quark content of the neutron in beta decay? (e) Quarks cannot exist on their own. What combinations are possible? 2. (a) Write down the names of the 6 leptons and arrange them into their usual 3 pairs. (b) Label each lepton with its electric charge in coulombs. (c) Which lepton is responsible for the science of chemistry? 3. (a) Name the 4 fundamental forces in nature and the Force-Carriers which are responsible for each one. (b) Which two have infinite range? (c) Which one allows beta decay to take place? (d) The chair you are sitting on is pushing back on you. Which of the fundamental forces is responsible for keeping you in your chair and which one is responsible for pushing back on you? (e) Which fundamental force holds the nucleus together?

3 Homework 2: Electric Fields and Potential Difference J of energy are used in moving a charge between two plates, across which there is a voltage of 50 volts. (a) How much charge was moved? (b) How many electrons have been moved? 2 A proton enters a simple particle accelerator as shown below. The p.d. across the plates of the accelerator is 25 kv. The proton is at rest at plate A. + - proton A B (a) What is the gain in kinetic energy of the proton as it reaches plate B? (b) Find the velocity of the proton when it hits plate B. 3 The diagram below shows a cathode ray tube used in an oscilloscope. The electrons which are emitted from the cathode start from rest and reach the anode with a speed of 4.2 x 10 7 m s -1. (a) (i) Calculate the kinetic energy in joules of each electron just before it reaches the anode. (ii) Calculate the p.d. between the anode and cathode. (b) Describe how the spot at the centre of the screen produced by the electrons can be moved to position X. Your answer must make reference to the relative sizes and polarity (signs) of the voltages applied to plates P and Q.

4 Homework 3 Radioactivity 1 The diagram shows the apparatus used by Rutherford to investigate the scattering of alpha particles by gold foil. From the observations made as the microscope and screen were moved from P to Q, Rutherford deduced that an atom has a nucleus which is : (A) positively charged (B) massive (C) much smaller than the volume of the atom Explain how the observations from the scattering experiment led to these three deductions 2 State the number of neutrons and protons in each of the following nuclei. i) N ii) 78 Pt iii) 13 6 C 3 Copy and complete the following decay chain showing the particles emitted and the missing element. 4 A radioactive source has 12 x 10 6 decays in one minute. Find its activity.

5 Homework 4 Fission and Fusion 1 Calculate the energy released from the neutron induced fission reaction shown below n + Pu 137 Te Mo n masses neutron : kg Plutonium-239 : kg Tellurium-137 : kg Molybdenum-100 : kg 2 Two deuterons (deuterium nuclei), fuse together as shown by the equation below. Find the energy released in this reaction. 2 H + 2 H 3 He n + energy masses: hydrogen-2 : kg neutron : kg helium-3 : kg Homework 5: The Photoelectric Effect Planck s constant, h = 6.63 x Js 1 The energy required to eject an electron from sodium is 2.9 x J. Calculate the wavelength of radiation needed to produce the photoelectric effect with sodium. Roughly, what colour is this light? 2 Find the number of photons per m 2 in a beam of irradiance 4 Wm -2 if the frequency of the radiation is 4.5 x Hz. 3 A photon of frequency 6.5 x Hz is incident on a metal whose work function is 4.64 x J. Will an electron be ejected?

6 Homework 6: Interference and Diffraction 1 In an experiment on interference of microwaves it is found that the distances from the slits to the first area of destructive interference is 39.2 cm and 37.7cm. What value does this give for the wavelength of the microwaves? 2 A diffraction grating with 300 lines/mm is illuminated with light from a laser. A second order maximum is obtained at an angle of 18 o to the straight through direction. Find a) The spacing of the grating in metres. b) The wavelength of the laser light. c) The angle at which the first order maximum will be observed. 3 Light of wavelengths 420 nm and 650 nm is incident on a diffraction grating having 600 lines/mm. Calculate the angular separation of the first order maxima. 4 A biologist is studying the effect of different colours of light on a sample of chlorophyll. She sets up the apparatus shown below, using a diffraction grating with 6 x 10 5 lines per metre to produce a first order spectrum of sunlight. a) Explain briefly how a diffraction grating produces a continuous spectrum from the ray of sunlight. b) The wavelength of the light at the end X of the spectrum is 410 nm. Calculate the value of the angle θ. c) The angle A in the diagram above is 9 o. Calculate the wavelength at end Y of the spectrum. d) The biologist now uses a triangular glass prism to produce a continuous spectrum from a ray of sunlight. State two difference between this spectrum and the spectrum produced by the grating.

7 Homework 7: Refraction and Total Internal Reflection 1 A ray of light enters water, refractive index 1.3, as shown in the diagram below. What is the size of the angle of refraction? 2 At what angle does the light leave the prism shown below? A swimming pool is illuminated by a lamp built into the bottom of the pool. Three rays of light from the same point in the lamp are incident on the water-air boundary with angles of incidence 30 o, 40 o and 50 o, as shown below. The refractive index of the water in the pool is a) Draw a diagram to show clearly what happens to each ray at the boundary. Indicate on your diagram the sizes of appropriate angles. All necessary calculations must be shown. b) An observer stands at the side of the pool and looks into the water. Explain, with the aid of a diagram, why the image of the lamp appears to be at a shallower depth than the bottom of the pool.

8 Homework 8: Light Irradiance 1 The illumination 2m from a lamp is 1000 lux. What will be the illumination at the following distances from the lamp? a) 4m b) 6m c) 1m d) 0.5m 2 Saturn is 10 times further away from the Sun than the Earth. How will the irradiance of sunlight on Saturn compare with that on Earth? 3 To improve the lighting in a room it is proposed to lower the lamps by 1m. By calculation investigate the savings that could be made. 4 A badly aligned laser, of power 0.1mW, has a beam diameter of 1mm which doubles in size for every metre travelled. Calculate the irradiance of the laser at a distance of 5m. 5 A laser is marked with the warning DANGER: EYE HAZARD. Why does this laser, which has a power output of only 0.20 mw, present a greater potential eye hazard than a 100 W lamp? In hospitals, pulsed lasers may be used to repair damage to the retina of the eye. The specification of a typical pulsed laser is given below: Gas used in laser Duration of pulse Energy of one pulse Wavelengths of laser light emitted : argon : 0.50 ms : 0.10 J : 488 and 514 nm The cross-sectional area of the laser beam at the retina is 1.5 x 10-9 m 2. Calculate the light irradiance produced at the retina during a pulse of light from this laser.

9 Homework 9: Spectra 1 The diagram below shows three possible energy levels in a hydrogen atom. Calculate the wavelength of the spectral lines with highest and lowest frequencies. How many lines could be produced? E x J. E x J. E x J. nucleus 2 (a) Laser light is monochromatic and coherent. Briefly explain the meaning of the terms monochromatic and coherent. (b) A laser radiates energy when electrons are stimulated to fall from energy level E 2 to energy level E 1 as shown in the diagram. (i) What are the frequency and wavelength of the radiation emitted? (ii) Name the section of the electromagnetic spectrum in which the radiation is found. (c) The beam of light from a laser is very intense. Give two reasons for this.

10 Homework 10: Absorption Spectra 1 (a) A sodium vapour lamp emits bright yellow light when electrons make transitions from one energy level to another within the sodium atoms. (i) State whether electrons are moving to higher or lower energy levels when the light is emitted. (ii) The wavelengths of the emitted light are nm and nm. Using Planck s constant, h = 6.63 x Js, calculate the energy difference between these two energy levels in the sodium atom. (b) A Bunsen flame containing vaporised sodium is placed between a sodium vapour lamp and a screen as shown. (i) Explain why a dark shadow of the flame is seen on the screen. (ii) The sodium vapour lamp is replaced with a cadmium vapour lamp. Explain why there is now no dark shadow in the flame on the screen.

Higher -o-o-o- Past Paper questions o-o-o- 3.4 Spectra

Higher -o-o-o- Past Paper questions 1991-2010 -o-o-o- 3.4 Spectra 1992 Q37 The diagram below shows the energy levels for the hydrogen atom. (a) Between which two energy levels would an electron transition