PHY3054 - Exam 3 - Fall 1996 - Selman Hershfield
1. If the distance to the moon is 3.85 x 108 m, how long does it take a radio signal to reach earth from the moon?

1. 10-3 s
2. 10-2 s
3. 0.1 s
4. 1 s
5. 10 s

2. You are listening to a radio station with wavelength is 3.3 m. Which station is it?

1. 91 FM
2. 100 FM
3. 101 FM
4. 910 AM
5. 1100 AM

3. Polarized light at an angle of 70 degrees and intensity I0 is incident from the left and passes sequentially through polarizers at angles 70, 130, and 60 degrees as indicated in Fig. 1. What is the intensity and polarization of the light exiting on the right? (Angles are measured from the vertical going counterclockwise.)

1. 0.012 I0
2. 0.015 I0
3. 0.018 I0
4. 0.024 I0
5. 0.030 I0

4. Two polarizers have polarization axes which are perpendicular to one another. A pair of polarized sunglasses is placed in between the polarizers. The sunglasses are rotated to maximize the intensity of the light transmitted through the combined polarizer - sunglasses - polarizer set-up. What is the minimum angle the sunglasses can be rotated so that the outgoing intensity is again maximized?

1. 45
2. 60
3. 90
4. 135
5. 180

5. Figure 3 shows refraction of light at the interface between material A and material B, and also at the interface between material C and material B. Assuming that the angle of the transmitted light is the same in both cases, which of the following is true for the indices of refraction for the three materials?

1. nA > nB > nC
2. nA > nC > nB
3. nB > nA > nC
4. nB > nC > nA
5. nC > nA > nB

6. In Fig. 2 light is incident from the left at -29 degrees relative to the horizontal. What is the angle of the exiting light relative to the horizontal?

1. -33 degrees
2. -46 degrees
3. -57 degrees
4. -63 degrees
5. -76 degrees

7. A person is looking down into the water from a boat as shown in Fig. 4. If n = 1.4 for salt water and n = 1 for air, which of the points, A through E, can the boater see? (List all of them.)

1. A and B
2. A, B, and C
3. A, B, C, and D
4. E
5. D and E

8. While SCUBA diving, you see a shark. The shark appears to you to be 10 meters away. In reality how much closer or further away is it? (Assume that you are wearing a mask and that there is air in the mask! Take the index of refraction of water to be 1.33 and of air to be 1.)

1. The shark is 3.33 m closer than you think.
2. The shark is 2.5 m closer than you think.
3. The shark is where you think it is.
4. The shark is 2.5 m further than you think.
5. The shark is 3.33 m further than you think.

9. Put your name, social security number, and test number correctly on the bubble sheet and the exam printout.

1. Done correctly.
2. Done incorrectly.
3. Done incorrectly.
4. Done incorrectly.
5. done incorrectly.

10. Draw a ray diagram to determine the position of the image created by the concave mirror shown in Fig. 6.

1. A
2. B
3. C
4. D
5. E

11. A convex mirror with radius 4 m is placed at the back of a store 30 m from the clerk. A customer who is 1.8 m tall stands 5 m from the mirror. Does the customer appear larger or smaller in the mirror than in real life? Does the customer's image in the mirror appear right-side-up or upside-down?

1. Smaller and right-side-up
2. Smaller and upside-down
3. Larger and right-side-up
4. Larger and upside-down
5. Same size and right-side-up

12. You have just finished getting a haircut and in order to see the back of your head, the person who cut your hair holds up a mirror as shown in Fig. 5. How far is the image of the back of your head in the small mirror from you? Hint: The first mirror produces an image which the second mirror reflects.

1. 0.3 m
2. 1.8 m
3. 3.0 m
4. 3.3 m
5. 3.6 m

13. Draw a ray diagram to determine the position of the image create by the diverging lens shown in Fig. 7.

1. A
2. B
3. C
4. D
5. E

14. A schematic of a slide projector is shown in Fig. 8. Light shines through the slide, goes through a converging lens, and produces an image on the wall. If the size of the slide (object) is 35 mm, the size of the image is 2 m, and the distance of the slide to the wall is 5 meters, how far is the slide from the lens?

1. 35 mm
2. 55 mm
3. 85 mm
4. 95 mm
5. 115 mm

15. A magnifying glass is held 0.5 m from a person's eye and 10 cm from a piece of paper. Figure 9 shows what the person sees with and without the magnifying glass. What is the focal length of the magnifying glass?

1. 4 cm
2. 6 cm
3. 10 cm
4. 20 cm
5. 30 cm

16. Two lenses are placed on the x-axis. The first lens is a converging lens with focal length 7 cm placed at x = -3 cm. The second lens is a diverging lens with focal length 11 cm placed at x = 6 cm. If an object is placed at x = -17 cm, what is the position of the image? (Choose the closest answer.)

1. x = 3 cm
2. x = 9 cm
3. x = 12 cm
4. x = 15 cm
5. x = 20 cm

17. A telescope is made of two lenses: a objective with focal length 1 m and an eyepiece with focal length 0.4 m. The objective and eyepiece are separated by 1.4 m. What is the angular size of a 1.8 m tall person 100 m away without the telescope and with the telescope?

1. 1 degree and 2.5 degrees
2. 1.4 degrees and 3.5 degrees
3. 2 degrees and 5 degrees
4. 2.8 degrees and 7 degrees
5. 18 degrees and 45 degrees

18. Two lenses are placed on the x-axis. The first lens is a converging lens with focal length 0.5 cm placed at x = -10 cm. The second lens is a converging lens with focal length 5 cm placed at x = 20 cm. If an object is placed at x = -10.51 cm, what is the net magnification of the image?

1. -10
2. -50
3. 50
4. -500
5. 500

19. In the previous question, what is the magnitude of the angular magnification assuming that the near point is 30 cm? Hint: This is a microscope.

1. 100
2. 200
3. 300
4. 400
5. 500

20. The furthest object a particular nearsighted person can see clearly is 1 m away. In order to correct for this, this person wears glasses. If the glasses are 0.5 cm from the eye, what kind of lenses should they wear?

1. Converging lens with f = 1 m
2. Diverging lens with f = 1 m
3. Converging lens with f = 1.1 m
4. Diverging lens with f = 1.1 m
5. Diverging lens with f = 0.9 m

1. Answer = (4) 1 s
2. Answer = (1) 91 FM
3. Answer = (5) 0.030 I0
5. Answer = (5) nC > nA > nB
6. Answer = (2) -46 degrees
7. Answer = (2) A, B, and C
8. Answer = (5) The shark is 3.33 m further than you think.
9. Answer = (1) Done correctly.