Physics 30: Chapter 5 Exam Wave Nature of Light Name: Date: Mark: /33 Numeric Response. Place your answers to the numeric response questions, with units, in the blanks at the side of the page. (1 mark each) 1. Determine the frequency of 300 nm light. 1.00 x 10 15 Hz 2. A laser pulse aimed from the Earth at a reflector on the Moon requires a total travel time of 2.71 s between the initial pulse and the detection of the reflected signal back on the Earth. Calculate the distance between the Earth and the Moon. 4.07 x 10 8 m 3. Light from air strikes the surface of water (n = 1.33) at an angle of 36 relative to the surface as it comes from the air. Calculate the angle of refraction. 37 4. Light falls on a pair of slits 1.30 µm apart. The maxima are measured to be 61.0 cm apart and the screen is a distance of 1.00 m from the slits. Determine the wavelength of light. 677 nm Kennedy 2008 1
Written Response. Show all your work. Clearly identify your final answer(s) rounded off to the proper number of significant digits. Most hand held lasers have a power rating of 0.5 mw. A more powerful 40 mw green laser is used with a DVD in order to determine its wavelength as shown in the diagram below. The DVD acts as a diffraction grating having a line spacing of 0.74 µm. screen Distance between first order bright fringes laser DVD Separation distance (cm) Distance between first order bright fringes (cm) 42.7 87.8 (43.9) 47.2 97.1 (48.6) 64.5 132.1 (66.1) 77.6 159.3 (79.7) 91.0 186.0 (93.0) Kennedy 2008 2
a. Plot the data in order to produce a straight line. (3 marks) Distance between first order bright spots as a function of Separation Distance Distance to Central Fringe (cm) 100 80 60 40 (45.0, 46.0) (90.0, 94.5) 40 60 80 100 Separation distance (cm) b. Use the graph to determine the wavelength of the green laser. (3 marks) The laser has a wavelength of 542 nm. Kennedy 2008 3
Multiple Choice. Select the best answer and mark it clearly on your Scantron. (1 mark each) 1. Identify the situation below that would produce electromagnetic radiation. a. An electron travelling at a constant speed b. A neutron accelerating from rest c. An electron travelling in a circle d. A neutron travelling in a circle 2. Select the list that has sections of the EMR spectrum ordered from lowest to highest energy. a. infrared, violet, red, X-rays b. radio, orange, blue, gamma c. X-rays, ultraviolet, blue, infrared d. Infrared, green, red gamma 3. An electromagnet wave is travelling to the north. Its magnetic component is vibrating eastwest. Its electric component must be vibrating a. up-down b. west-east c. north-south d. south-north 4. Calculate the period of the wave for a blue laser diode having a frequency of 4.24 x 10 14 Hz. a. 4.24 x 10-14 s b. 7.08 x 10-7 s c. 4.24 x 10-15 s d. 2.36 x 10-15 s 5. A physics teacher orders a new pen laser that has a wavelength of 460 nm. The location in the spectrum of the laser beam produced by this pen laser is most likely a. red b. orange c. blue d. ultraviolet 6. Determine the time required for a radio signal to reach Earth if it was sent from Mars which is a distance of 7.80 x 10 10 m when it is closest to the Earth. a. 260 s b. 3.85 ms c. 2.34 x 10 19 s d. 130 s Kennedy 2008 4
7. Identify the graph that best communicates the frequency of an electromagnet wave as a function of wavelength. a. b. wavelength wavelength c. d. wavelength wavelength 8. A laser requires a time of 620 ms to travel from its source, bounce off a distant reflector and return to the source. Determine the separation distance between the source and reflector. a. 1.86 x 10 8 m b. 9.30 x 10 7 m c. 1.08 x 10-8 m d. 2.16 x 10-8 m 9. Armand Fizeau used a spinning wheel rotating at 12.5 Hz, which showed that the light travelled the 8.63 km separating the wheel and a reflecting mirror, and back in a time of 5.5 x 10-5 s. Calculate the speed of light as determined by Fizeau. a. 1.6 x 10 8 m/s b. 2.9 x 10 8 m/s c. 3.0 x 10 8 m/s d. 3.1 x 10 8 m/s Kennedy 2008 5
Use the information below to answer questions 10 & 11. Albert Michelson used a rotating mirror and a plane mirror, as shown in the diagram below, to precisely determine the speed of light. This allowed a pulse of light to be reflected and observed at the detector only when the rotating mirror rotated at a proper frequency. Light source Rotating mirror Plane mirror Observer (detector) 10. Determine Michelson s value for the speed of light using an 8-sided mirror rotating at 526.5 Hz placed 35.51 km from the plane mirror. a. 2.996 x 10 8 m/s b. 2.991 x 10 8 m/s c. 3.000 x 10 8 m/s d. 3.100 x 10 8 m/s 11. Determine the separation distance between Michelson s rotating 8-sided mirror and the plane mirror if the mirror must be rotating at 624.5 Hz to allow the observer to detect the reflected light pulse. a. 15.0 km b. 30.0 km c. 60.0 km d. 120 km 12. A ray of light from air, having a refractive index of 1.00, is incident on the surface of a block of glass, having a refractive index of 1.50, at an angle of 37.6. Determine the angle of refraction. a. 36.0 b. 42.0 c. 24.0 d. 48.0 13. Light travelling from air enters a layer of a clear liquid. The speed of light through the liquid is 2.75 x 10 8 m/s. Calculate the liquid s index of refraction relative to air. a. 0.917 b. 1.09 c. 2.75 d. 1.00 Kennedy 2008 6
14. As a light wave crosses the boundary between two different mediums, its remains constant. a. speed b. frequency c. angle d. wavelength 15. The speed of light in a clear liquid is 0.80 the speed of light in air. The critical angle of the liquid is a. 0.93 b. 37 c. 53 d. 90 16. Diffraction may be defined as the amount of a. bending as a wave passes from one substance to another b. bending as a wave passes through an opening c. frequency shift when a wave passes from one substance to another d. frequency shift as a wave passes through an opening 17. A grating is ruled with a line density of 5400 lines/cm. Monochromatic light striking the grating forms a second order image diffracted at 45.0. Determine the wavelength of the light used. a. 655 nm b. 131 nm c. 1.31 x 10-4 m d. 6.55 x 10-5 m 18. Monochromatic light of 530 nm is passed through two narrow slits imprinted onto a slide. The distance between the two slits is 0.75 mm and the screen is located 120 cm away from the slide. Determine the separation distance between bright lines in the interference pattern formed on the screen. a. 1.2 mm b. 0.85 mm c. 0.35 mm d. 0.29 mm Kennedy 2008 7
19. Determine the angle of deviation of the second order maxima produced when monochromatic light of 640 nm is directed through two slits that are 6.43 µm apart. a. 11.5 b. 5.71 c. 53 d. 37 20. Identify the phenomena below that does not support the idea that light is a wave. a. Polarization b. Diffraction c. Motion through a vacuum d. Constructive and destructive interference 21. A visible spectrum is produced using white light and a glass prism. The colour that demonstrates the greatest deviation from its original path is a. red b. green c. blue d. violet 22. Dispersion may be defined as the a. separation of wavelengths due colour absorption b. separation of wavelengths due to refraction c. production of constructive interference d. production of destructive interference 23. A polarizing filter a. filters out all light except wavelengths that are oriented with the filter b. causes light to behave like a particle reflecting between two mirrors c. generates electromagnetic fields d. releases energy in the form of EMR in all directions Kennedy 2008 8
Stats Class average on multiple choice: 83 % Question Answer % Correct Question Answer % Correct 1 C 40 16 B 60 2 B 93 17 A 77 3 A 90 18 B 90 4 D 100 19 A 97 5 C 63 20 C 73 6 A 93 21 D 67 7 A 90 22 A 80 8 B 90 23 A 83 9 E 87 10 B 90 11 B 67 12 C 100 13 B 97 14 B 90 15 C 87 Kennedy 2008 9