There were 4 different versions of the exam. The versions had the same questions and answers, but the order of the answers was different in each version. The correct answer to each question is identified by an asterisk in the following text.

Each correct answer counts 5 points and there is no partial credit.

1. A wavelength of 633 nm is numerically equivalent to

(*) 0.633 mm and 633 x 10^-9 m

() 0.633 mm and 63.3 x 10^-8 m

() 0.0633 m and 633 x 10^-4 m

() 6.33 mm and 63.3 x 10^-5 m

() none of the above

2. Using the speed of light in vacuum, calculate how long it takes a light signal to travel on a straight line from Denver to New York, a distance of 2,000 km.

(*) 6.6 x 10^-3 s

() 0.66 s

() 6.6 x 10^-6 s

() 3.3 x 10^-3 s

() 13.2 x 10^-3 s

3. A radio wave whose wavelength is 1 m strikes the roadway in front of the Physics building and is reflected. We would expect that:

(*) l/D is less than 1 so that geometrical optics applies to the reflection

() l/D is greater than 1 so that geometrical optics does not apply to the reflection

() l/D is less than 1 so that geometrical optics does not apply to the reflection

() l/D is greater than 1 so that geometrical optics applies to the reflection

() l/D is approximately 1 so that this is a transitional case

4. Radio Station KGNU broadcasts at a frequency of 88.5 MHz (88.5 x 10⁶ Hz). The wavelength of this signal is about

(*) 3.4 m

() 3.4 km

() 34 m

() 1.8 m

() 1.8 km

The figure on the next page shows a light wave field as a function of time at a single point in empty space. Use this figure to answer questions 5-8.

5. The numerical value for the amplitude of the wave shown in the figure is:

(*) 10

() 20

() 4

() 2 x 10^-12

() 4 x 10^-12

6. The numerical value for the period of the wave shown in the figure is:

() 5

() 10

() 20

() 2 x 10^-12

(*) 4 x 10^-12

7. The frequency of the wave shown in the figure is:

(*) 25 x 10¹⁰ Hz

() 250 x 10⁸ Hz

() 25 MHz

() 250 MHz

() None of the above

8. Which of the following statements is true (choose only one answer)?

(*) I can determine the wavelength of this wave from the information given

() I also need the index of refraction to determine the wavelength

() I can determine the polarization of the wave from the information given

() I also need the intensity of the wave to determine the wavelength

() If the frequency of the wave were doubled, the wavelength would also double

9. Which of the following statements is true (choose only one answer)?

(*) The magnification of a pinhole camera increases when the screen used to display the image is moved further away from the pinhole (leaving everything else the same).

() The magnification of a pinhole camera increases when the object is moved further away from the pinhole (leaving everything else the same).

() The image produced by a pinhole camera is always the same size as the object, but is inverted.

() The magnification of a pinhole camera depends on the wavelength of the light that is used to illuminate the object.

() The magnification of a pinhole camera depends on the size of the pinhole

10. If the index of refraction of a medium is 1.25, the speed of light in that medium is

(*) 240,000 km/s

() 260,000 km/s

() 220,000 km/s

() 240,000 m/s

() none of the above

11. The critical angle at the interface between air and glass is

() larger for blue light than for red light because the index of refraction for blue large in glass is larger

(*) smaller for blue light than for red light because the index of refraction for blue light in glass is larger

() larger for blue light than for red light because the index of refraction for blue light in air is larger

() smaller for blue light than for red light because the index of refraction for blue light in air is smaller

() the same for blue light and red light

12. To measure the critical angle at a glass-air interface you would

() monitor the angle of refraction in the glass as you vary the angle of incidence on the air side of the boundary

(*) monitor the angle of refraction in air as you vary the angle of incidence on the glass side of the boundary

() monitor the angle of reflection in air as you vary the angle of incidence in air

() monitor the amplitude of the reflected light in the air as you vary the angle of incidence in air

() compare the angle of incidence for blue light in glass with the angle of incidence for red light in air

13. The product of the frequency and the wavelength of a light wave is

() always equal to the velocity of propagation of light in vacuum

() equal to the velocity of propagation only when light is traveling in a vacuum

(*) equal to the velocity of propagation in whatever medium the light is in

() equal to the index of refraction

() equal to the product of the index of refraction and the velocity of light in vacuum

14. A black body is heated to a high temperature and then allowed to cool. As it cools

() The emitted power and the peak wavelength both decrease

() The emitted power and the peak wavelength both increase

(*) the emitted power decreases and the peak wavelength increases

() the emitted power increases and the peak wavelength decreases

() the emitted power decreases and the peak wavelength remains unchanged

15. If a pulse of red light and a pulse of blue light travel in vacuum

() The red pulse travels faster because its index of refraction is smaller

() The blue pulse travels faster because its index of refraction is larger

(*) The two pulses travel at the same speed

() The relative speed depends on the exact wavelengths of the red and blue pulses

() The relative speed depends on the polarization of the two pulses

16. If a light wave is traveling in vacuum and its period is doubled then

() its frequency and its wavelength both double

() its frequency and its wavelength are both halved

(*) its frequency is halved and its wavelength is doubled

() its frequency is doubled and its wavelength is halved

() its frequency and its wavelength both increase by the square root of 2

17. When light traveling in air strikes a clean glass surface exactly along the normal to the surface

() the reflected light has a phase shift of 180 degrees and the amplitude of the refracted beam is about 50%

() the reflected light has no phase shift and the amplitude of the refracted beam is about 50%

(*) the reflected light has a phase shift of 180 degrees and the amplitude of the reflected beam is about 4%

() the reflected light has a no phase shift and the amplitude of the reflected beam is about 4%

() the reflected light has a phase shift of 90 degrees and the amplitude of the reflected beam is about 4%

18. When an opaque object is illuminated by an extended source

() The umbra in the shadow is larger than the penumbra

(*) The umbra in the shadow is smaller than the penumbra

() There is a penumbra but never an umbra in the shadow

() There is an umbra but never a penumbra in the shadow

() The size of the shadow depends on the index of refraction of the object

19. When light traveling in air strikes a glass surface at a large angle of incidence

(*) the fraction that is reflected approaches 100%

() the fraction that is refracted approaches 100%

() the fraction that is reflected approaches 50%

() the fraction that is reflected approaches 100% for blue light only

() the fraction that is reflected approaches 100% for red light only

20. A student measures the frequency and the wavelength of a light beam traveling in a medium and obtains the values 522 x 10¹² Hz for the frequency and 479 nm for the wavelength. The index of refraction of this medium is about

(*) 1.2

() 1.3

() 1.1

() 2.0

() none of the above