Question 1

An object is placed 60 cm in front of a mirror and the image is upright and ¼ the size of the object. What is the focal length of the mirror?

Accepted Answer

A)   −12 cm
B)   −20 cm
C)   −45 cm
D)   −75 cm
E)   some positive value not given B

Question 2

A laser beam is directed at a horizontal glass surface with an angle of incidence of 57 degrees. If the angle of refraction is 38 degrees, at what incident angle will the reflected beam be fully polarized?

Accepted Answer

A)   46°
B)   36°
C)   54°
D)   43° C

Question 3

A light ray in material 1 goes into material 2. The angle of incidence in material 1 is 40.0° and the angle of refraction in material 2 is 31.0°. If the index of refraction of material 1 is 1.60, what is the index of refraction of material 2?

Accepted Answer

A)   3.20
B)   2.00
C)   1.88
D)   1.41
E)   1.20 B

Question 4

A 25 cm focal length mirror has a 3.0 cm tall object placed 20 cm in front of it. What is the size of the image and is it upright or inverted?

Accepted Answer

A)   1.0 cm, upright
B)   3.8 cm, inverted
C)   2.4 cm, inverted
D)   15 cm, upright
E)   12 cm, upright

Question 5

When you see your image in a plane mirror, your image appears to be

Accepted Answer

A)   in front of the mirror.
B)   at the surface of the mirror.
C)   behind the surface of the mirror at a distance equal to your distance from the mirror.
D)   behind the surface of the mirror at a distance equal to half your distance from the mirror.

Question 6

In order to produce an image twice the size of an object with a converging lens of focal length f, what object distance should be used?

Accepted Answer

A)   f
B)   f/2
C)   2f
D)   2f/3
E)   3f/2

Question 7

The critical angle for Lucite is 41.8°. What is Brewster's angle for Lucite?

Accepted Answer

A)   33.7°
B)   26.3°
C)   48.2°
D)   56.3°
E)   Brewster's angle does not exist for this material

Question 8

You are conducting an experiment with a converging lens and have set it up to produce a real image of a distant tree. If you cover the top half of the lens with opaque paper, what occurs?

Accepted Answer

A)   The bottom half of the image is missing.
B)   Nothing happens.
C)   The image becomes half as large.
D)   The image is complete, but dimmer than it was.
E)   The top half of the image is missing.

Question 9

A convex mirror has a radius of 10 cm. What is its focal length?

Accepted Answer

A)   10 cm
B)   5.0 cm
C)   20 cm
D)   −5.0 cm
E)   −10 cm

Question 10

A concave mirror has a 12 cm tall object placed 40 cm in front of it. An image forms 60 cm in front of the mirror. What is the size and orientation of the image?

Accepted Answer

A)   8.0 cm, inverted
B)   8.0 cm, upright
C)   18 cm, inverted
D)   18 cm, upright
E)   24 cm, upright

Question 11

A diver below the surface of a lake notices that no light appears to be coming toward her from angles greater than θ, measured from the vertical. If the index of refraction of water is 1.33, what is the angle θ?

Accepted Answer

A)   30.0°
B)   36.9°
C)   41.2°
D)   48.8°
E)   53.1°

Question 12

A light ray goes through two thick rectangular slabs of glass, each of the same uniform thickness. The first slab has index of refraction n1 and the second n2. If n1 2. How does the original angle of incidence θi into the first slab compare to the final angle of refraction θf where the ray leaves the second slab going back into air?

Accepted Answer

A)   θi > θf
B)   θi f
C)   θi = θf
D)   θi = (n1/n2) θf
E)   more information is needed

Question 13

An innovative physics professor conducts laboratory exercises in the college swimming pool. The professor places a submersible laser under water (n = 1.3) and aims the beam at a block of glass (n = 1.5), which is also under water. At what angle of incidence will the reflected beam be totally polarized?

Accepted Answer

A)   61°
B)   49°
C)   41°
D)   39°

Question 14

A building 30 m tall is being photographed with a camera with a lens of focal length 50 mm. How tall is the image if the building is 100 m away?

Accepted Answer

A)   30 mm
B)   15 mm
C)   10 mm
D)   3.0 mm
E)   1.0 mm

Question 15

A 6.0 cm tall object is placed 20 cm in front of a convex mirror with focal length −100 cm. Where is the image formed?

Accepted Answer

A)   80 cm behind the mirror
B)   25 cm behind the mirror
C)   17 cm behind the mirror
D)   17 cm in front of the mirror
E)   25 cm in front of the mirror

Question 16

If an object is placed before a single thin lens

Accepted Answer

A)   real images are always enlarged.
B)   virtual images are always inverted.
C)   real images are always inverted.
D)   convex lenses never create virtual images.

Question 17

When looking at your own reflection in a plane mirror, you notice that you can't see your whole body. You adjust the position of the mirror on the wall, but you still can't see yourself completely. In order to see a larger fraction of your body, what could you do?

Accepted Answer

A)   can do nothing about it with this mirror
B)   get farther from the mirror
C)   tilt the mirror
D)   get closer to the mirror

Question 18

Fiber optic cable is in the form of a cylindrical core of fiber with index of refraction 1.67 surrounded by a layer of cladding of index 1.45. What is the maximum angle for light rays inside the fiber core with respect to the cable's axis for which the light will be fully transmitted thanks to total internal reflection?

Accepted Answer

A)   29.7°
B)   60.3°
C)   36.8°
D)   53.2°

Question 19

Which of these statements is true for the image formed by an object placed in front of a thin lens?

Accepted Answer

A)   Convex lenses never produce virtual images.
B)   Real images are always enlarged.
C)   Real images are always inverted.
D)   Virtual images are always inverted.

Question 20

Specular reflection occurs whenever

Accepted Answer

A)   rays reflect from a surface.
B)   rays reflect in all directions from a surface.
C)   rays reflect at only one angle from a surface.
D)   parallel rays all reflect at the same angle from a surface.
E)   visible light rays reflect.

Exam 23: Reflection and Refraction of Light