PHYS2002 – Spring 2012 – Practice Exam 3 (Chs. 25, 26, 27)

Constants

2

229

7

2212o

19

19

31

27

m/s 8.9

C/mN1099.8

m/AT 104

mN/C1085.8

C10602.1

C10602.1

kg1011.9

kg1067.1

=

⋅×=

⋅×=

⋅×=

×−=

×+=

×=

×=

−

−

−

−

−

−

g

k

q

q

m

m

o

e

p

e

p

πμ

ε

1. A convex mirror can form which of the following images:

A) virtual, upright, reduced B) virtual, upright, enlarged C) real, inverted, reduced D) real, inverted, enlarged E) more than one of the other choices

2. For any single spherical mirror, a virtual image is:

A) always inverted B) always upright C) sometimes upright and sometimes inverted D) None of the above

3. The figure below shows three laser beams with the same wavelength traveling in

a liquid of unknown composition with index of refraction n. The beams strike a boundary with air, and Laser B is completely reflected back into the liquid as shown. Which statement best describes what happens to Lasers A and C?

A) A and C are totally internally reflected. B) Neither A nor C is totally internally reflected. C) A is totally internally reflected, but C is not. D) A is not totally internally reflected, but C is. E) A is totally internally reflected, but whether C is totally internally reflected

depends on the value of n.

4. An object (the arrow) is located to the left of a converging lens as shown below.

The focal points of the lens are marked as F. At what point A, B, C, D, or E is the image formed?

Laser A

Laser B Laser C

Laser B

liquid

air

A B C D E F F

Object

Lens

5. What could you do to improve the optical resolution of a microscope?

A) Increase the wavelength of the light. B) Increase the diameter of the lens. C) Decrease the wavelength of the light. D) Both A and B. E) Both B and C.

6. A thin layer of oil floating on water will often appear multicolored. Which of the following processes explains why this happens? Choose the best answer.

A) Reflection, refraction and diffraction B) Refraction, diffraction and polarization C) Refraction, diffraction and interference D) Reflection, refraction and interference E) Refraction, polarization and interference

7. A coin is placed 8.0 cm in front of a concave mirror. The mirror produces a real and inverted image that has a diameter 4.0 times larger than that of the coin. What is the image distance?

A) 0.5 cm B) 2.0 cm C) 6.4 cm D) 32 cm E) None of the above.

8. When an object is placed 12 cm to the left of a lens, the image appears 6.0 cm to the left of the lens. What is the focal length of the lens?

A) -4 cm B) +4 cm C) -8.3 cm D) -12 cm E) None of the above.

9. You are looking down from above at a room that is 3 m × 3 m square. A laser sits

in the middle of the south wall and fires a beam of light that reflects off a plane mirror hanging on the east wall. Upon reflection, the beam then strikes a target located at the northwest corner (see figure). What is θ (the angle between the incident beam and the south wall)?

A) 30o B) 33.7o C) 36.9o D) 45o E) None of the above.

10. Vertical light rays of red light (wavelength = 660 nm) and violet light (wavelength = 410 nm) are incident on a glass prism as shown. The indices of refraction in the glass for the red and violet light are 1.651 and 1.703, respectively. The colors can emerge from the glass prism along 2 possible paths. Which color(s) took Path 1?

A) Red B) Violet C) Both colors took Path 1 D) Both colors took Path 2

11. A light ray travelling in Material A strikes the interface with Material B at the Brewster’s angle, which in this case is θ = 30°. What would be the Brewster’s angle for a light ray travelling in Material B and then striking the interface with Material A?

A) 30o B) 45o C) 60o D) 70o E) There can’t be a Brewster’s angle for this situation.

90o

90o 28.0o

Red andViolet Light

1 2

A

B

θ

Laser

South Wall

North Wall

East Wall

West Wall

Mirror

Target

θ

3.0 m

3.0 m

1.5 m

12. I am farsighted, and the prescription on the box of my contact lenses says +2.0 D. With my contacts on, I can read a book held 25 cm from my eye, but not any closer. How far away do I have to hold the book if I’m not wearing my contacts? In other words, how far away is my nearpoint from my eye?

A) 12.5 cm B) 25 cm C) 50 cm D) 100 cm E) None of the above

13. Doh. While jogging around the lake I accidentally drop my keys in the water. While looking for them I shine a light on the surface of the lake at an angle of 30° to the normal as shown. What’s the angle of refraction of the light ray in the water?

A) 15° B) 22° C) 30° D) 42° E) 60°

14. An object (the arrow) is located to the left of a converging lens at a distance from the lens that is 40% of its focal length as shown in the figure below. What is the magnification and orientation of the image formed?

A) m = +1.67 (upright) B) m = +1.00 (upright) C) m = +0.33 (upright) D) m = -0.33 (inverted) E) m = -1.67 (inverted)

15. In a Young’s double slit experiment, two slits with a separation distance of 8.5 × 10-5 m create an interference pattern on a screen 2.3 m away. If the 10th bright fringe above the central bright fringe is located 12 cm above it, what is the wavelength of the light being used in the experiment? Feel free to use the small angle approximation: sinθ ≈ tanθ.

A) 492 nm B) 440 nm C) 850 nm D) 920 nm E) None of these.

Air

Water n=1.33

30o

F F

Object

16. A beam of blue light (λvacuum = 465 nm) strikes a thin film of soap of thickness t resting on a diamond surface (see figure). The indices of refraction for air, soap, and diamond are 1.00, 1.33, and 2.42, respectively. What is the smallest nonzero thickness for the soap film, such that it appears dark?

A) 87 nm B) 116 nm C) 350 nm D) 465 nm E) None of the above.

17. In low light, a cat’s pupils, which are slit-shaped in bright light, open to a large circular diameter of about 12 mm. How close (r) would my cat Socola have to be in order to just resolve two mice separated by a distance of 5 cm? Assume Socola is watching the mice in red light, which has a wavelength of 630 nm in his eye.

A) 7.8 × 107 m B) 3.2 × 10-6 m C) 78 m D) 780 m E) None of the above.

nair = 1.00

nsoap = 1.33

ndiamond = 2.42

eye

t

5 cm

r

r