Chapter 7

Light is incident on a plane mirror at an angle of \(40^{\circ}\) relative to the normal. What is the angle of reflection?

Light is incident on a plane mirror at an angle of \(30^{\circ}\) relative to its surface. What is the angle of reflection?

Show that for a person to see his or her complete (head-to-toe) image in a plane mirror, the mirror must have a length (height) of at least one-half a person's height (see Fig. 7.4 ). Does the person's distance from the mirror make a difference? Explain.

How much longer must the minimum length of a plane mirror be for a 6 -ft 4 -in. man to see his complete head-to-toe image than for a 5 -ft 2 -in. woman to do so?

If a material has an index of refraction of \(1.45,\) what is the speed of light in the material?

The speed of light in a particular type of glass is \(1.40 \times 10^{8} \mathrm{m} / \mathrm{s}\). What is the index of refraction of the glass?

What percentage of the speed of light in vacuum is the speed of light in water?

The speed of light in a certain transparent material is \(41.3 \%\) of the speed of light in vacuum. What is the index of refraction of the material? (Can you identify the material?)

Sketch a ray diagram for a concave mirror with an object at \(D_{\circ}=R\) and describe the image characteristics.

Sketch ray diagrams for a concave mirror showing objects at (a) \(D_{o} > R,\) (b) \(D_{o} > f\), and (c) \(D_{o} < f\). Describe how the image changes as the object is moved toward the mirror.

An object is placed \(30 \mathrm{cm}\) from a convex spherical mirror with a focal length of \(20 \mathrm{cm} .\) Estimate where the image is located and what its characteristics are.

A reflecting, spherical Christmas tree ornament has a diameter of \(8.0 \mathrm{cm} .\) A child looks at the ornament from a distance of \(15 \mathrm{cm} .\) Describe the image she sees.

Sketch a ray diagram for a spherical convex lens with an object at \(D_{o}=2 f\) and describe the image characteristics.

Sketch ray diagrams for a spherical convex lens with objects at (a) \(D_{o} > 2 f,(\mathrm{b}) 2 f > D_{o} > f,\) and (c) \(D_{o} < f .\) Describe how the image changes as the object is moved closer to the lens.

An object is placed \(60 \mathrm{cm}\) in front of a converging lens with a focal length of \(20 \mathrm{cm} .\) Draw a ray diagram. Estimate the image distance and give the image characteristics.

An object is placed in front of a converging lens at an object distance of twice the focal length of the lens. Sketch a ray diagram and compare the image and object distances. Repeat with two more ray diagrams, using different focal lengths and still making the object distance twice the focal length. Can you draw any conclusions by comparing the object distance and the image distance?

A spherical concave lens has a focal length of \(20 \mathrm{cm},\) and an object is placed \(10 \mathrm{cm}\) from the lens. Draw a ray diagram. Estimate the image distance and give the image characteristics.

A particular convex lens has a focal length of \(20 \mathrm{cm},\) and an object is placed at the focal point. Draw a ray diagram and comment on where the image is formed.