### Problems

#### 16.1 Reflection

Some telephoto cameras use a mirror rather than a lens. What radius of curvature is needed for a concave mirror to replace a 0.800 -m focal-length telephoto lens?

- 0.400 m
- 1.60 m
- 4.00 m
- 16.0 m

What is the focal length of a makeup mirror that produces a magnification of 2.00 when a person’s face is 8.00 cm away?

- –16 cm
- –5.3 cm
- 5.3 cm
- 16 cm

#### 16.2 Refraction

An optical fiber uses flint glass (*n* = 1.66) clad with crown glass (*n* = 1.52) . What is the critical angle?

- 33.2°
- 23.7°
- 0.92 rad
- 1.16 rad

Suppose this figure represents a ray of light going from air (*n* = 1.0003) through crown glass (*n* = 1.52) into water, similar to a beam of light going into a fish tank.

Calculate the amount the ray is displaced by the glass (Δx), given that the incident angle is 40.0° and the glass is 1.00 cm thick.

- 0.839 cm
- 0.619 cm
- 0.466 cm
- 0.373 cm

#### 16.3 Lenses

A camera’s zoom lens has an adjustable focal length ranging from 80.0 to 200 mm . What is its range of powers?

- The lowest power is 0.05 D and the highest power is 0.125 D.
- The lowest power is 0.08 D and the highest power is 0.20 D.
- The lowest power is 5.00 D and the highest power is 12.5 D.
- The lowest power is 80 D and the highest power is 200 D.

Suppose a telephoto lens with a focal length of 200 mm is being used to photograph mountains 10.0 km away. (a) Where is the image? (b) What is the height of the image of a 1,000-m-high cliff on one of the mountains?

- (a) The image is 0.200 m on the same side of the lens. (b) The height of the image is – 2.00 cm.
- (a) The image is 0.200 m on the opposite side of the lens. (b) The height of the image is – 2.00 cm.
- (a) The image is 0.200 m on the opposite side of the lens. (b) The height of the image is +2.00 cm.
- (a) The image is 0.100 m on the same side of the lens. (b) The height of the image is +2.00 cm.