Physics- Chapter 20 Review

Which of the following is NOT a property of the images formed by a plane mirror?

• The image is located behind the mirror.

• The images are a result of specular reflection.

• The magnification is 1

• the image distance is equal to the object distance (although it may be negative).

• The image is smaller than the object.

Answer explanation

A plane mirror forms images that are the same size as the object.

Ray X strikes a flat mirror at an angle of θ = 28 degrees. What is the angle of incidence

• 62 °

• 150 °

• 120 °

• 90 °

• 28 °

Answer explanation

The angle of incidence is measured relative to the normal therefore in this case it is 90° - 28.0° = 62.0°.

 The radius of curvature of a spherical mirror is 70 cm. What is the focal length of the mirror?

• 110 cm

• 18 cm

• 70 cm

• 35 cm

• 4.0 cm

Answer explanation

f=R/2

70 cm/2=35 cm

On a bright and sunny day, a pedestrian notices his faint image in a shop window. Why did he see his image in the glass?

• Some of the light passed through the glass.

• Some of the light was reflected off of the glass.

• Some of the light was red.

• Some of the light was diffracted by the glass.

• Some of the light was refracted by the glass.

Answer explanation

Some of the light was reflecting off of the surface of the glass, while some of the light was passing through the glass (and, presumably, a little bit of light was absorbed by the glass, too).

Skiers will often wear sunglasses because much of the sunlight that strikes snow is

• absorbed

• diffracted

• reflected

• conducted

• transmitted

Answer explanation

Much of the sunlight reflects off of snow, which is why snow appears bright white.

A 40-cm-wide object seen through an optical device appears inverted and 20 cm wide. What is the magnification of the optical device?

• 2.0

• 0.50

• -0.50

• 1.0

• -1.0

Answer explanation

The size of the image is h_i = 20 cm and the size of the object is h_o = 40 cm.

−hi/ho=−20 cm/40 cm

A solar panel measures 3.0 × 8.0 m in size and collects energy at a rate of 16800 W in full sunlight. What is the intensity of the sunlight falling on the panel? (Assume the panel is 100% efficient.)

• 24 W/m²

• 1900 W/m²

• 700 W/m²

• 260 W/m²

• 17000 W/m²

Answer explanation

Intensity is power per unit area, or P ÷ A. For this problem the area is 3.0 m × 8.0 m = 24 m². The intensity is then 16800 ÷ 24 = 700 W/m².

A place in space where multiple rays from one point on an object come together again in a point is called a

• real image.

• refracted ray.

• real object.

• virtual object.

• virtual image.

Answer explanation

A real image is a point in space where many rays that leave one point on an object come together again.

Which of the following optical devices uses refraction?

I. mirror

II. lens

III. prism

• I and III only

• II and III only

• I, II, and III

• I and II only

• II only

Answer explanation

Mirrors use reflection; lenses and prisms use refraction.

What property of light explains the formation of shadows?

• Light can vary in intensity.

• Light can change direction.

• Light travels in straight lines.

• Light travels fast.

• Light carries energy and information.

Answer explanation

Shadows show that light travels in straight lines since they would form differently if light were able to curve around objects.