Question 1

A solar cooker uses a concave mirror to focus sunlight onto a pot. What is the main optical principle that allows the mirror to concentrate sunlight at a single point?

Accepted Answer

The focusing property of a concave mirror, which brings parallel rays to a focal point.

Question 2

Which equation correctly relates the focal length $$f of a $$thin lens to the radii of curvature $$R_1$$ and $$R_2$$ and the index of refraction $$n of $$the lens material?

Accepted Answer

$$\frac{1}{f} = (n-1) \left( \frac{1}{R_1$} - \frac{1}{R_2$} \right)$$

Question 3

A person with myopia uses a concave lens of focal length $$-0.50 m. $$What is the power of the lens in diopters?

Accepted Answer

$$-2.0 D$$

Question 4

When light passes from air ($$n=1.00) $$into water ($$n=1.33$$), which law describes the change in direction of the light ray?

Accepted Answer

Snell's law: $$n_1$$ \sin \$$theta_1$$ = $$n_2$$ \sin \$$theta_2$$

Question 5

A ray of light travels from medium 1 ($$n_1) $$into medium 2 ($$n_2) $$and then into medium 3 ($$n_3$$), with $$n_1$$ \u003e $$n_2$$ \u003e $$n_3. $$Which statement is true about the speed of light in these media?

Accepted Answer

The speed of light increases as the index of refraction decreases.

Question 6

A converging lens is used to form an image of an object. Which statement is always true for a real image formed by a single converging lens?

Accepted Answer

The image is inverted and can be projected onto a screen.

Question 7

The power $$P of a $$lens is defined as the inverse of its focal length $$f (in $$meters). What is the SI unit of lens power?

Accepted Answer

Diopter (D)

Question 8

A ray diagram for a thin lens uses three principal rays. Which ray passes through the center of the lens and is not deflected?

Accepted Answer

The ray that passes through the optical center of the lens.

Question 9

A plano-convex lens with $$n = 1.55 is to $$have a focal length of $$16.3 cm. $$What is the radius of curvature $$R of $$the convex surface if the plane side has infinite radius?

Accepted Answer

Question 10

A $$+7.00 D $$lens is held $$12.5 cm $$from an ant $$1.00 mm $$high. What is the image distance $$d_i$$?

Accepted Answer

$$d_i = 0.143 m$$

Question 11

If the critical angle for a liquid-air surface is $$47.2^\circ$$, what is the index of refraction $$n of $$the liquid?

Accepted Answer

$$n = \frac{1}{\sin 47.2^\circ}$$

Question 12

A diverging lens always produces which type of image for a real object?

Accepted Answer

Upright and virtual

Question 13

Sunlight is observed to focus at a point $$16.5 cm $$behind a lens. What is the power of the lens in diopters?

Accepted Answer

$$P = \frac{1}{0.165} = 6.06 D$$

Question 14

Which phenomenon explains why light remains inside an optical fiber and does not escape through the sides?

Accepted Answer

Total internal reflection

Question 15

A sharp image is located $$391 mm $$behind a $$215 mm $$focal length converging lens. What is the object distance $$d_o$$?

Accepted Answer

$$d_o = \frac{1}{\frac{1}{f} - \frac{1}{d_i}}$$

Question 16

When moonlight strikes the surface of a calm lake, what happens to the light?

Accepted Answer

Some of it reflects back to the air; some enters the water.

Question 17

If you look at a stone in a stream from above, where does it appear to be?

Accepted Answer

At a shallower depth than its actual depth due to refraction.

Question 18

Which formula gives the magnification $$M of a $$lens?

Accepted Answer

$$M = \frac{h_i}{h_o} = -\frac{d_i}{d_o}$$

Question 19

Both surfaces of a double convex lens have radii of $$34.1 cm. If $$the focal length is $$28.9 cm$$, what is the index of refraction $$n of $$the lens material?

Accepted Answer

$$n = 1 + \frac{R}{2f}$$

Geometric Optics: Fundamentals and Applications

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