Question 1

Which of the following statements best describes the ray model of light as used in everyday optics?

Accepted Answer

Light rays travel in straight lines through a vacuum or transparent material and do not interact with each other.

Question 2

A laser beam passes from air (n = 1.00) into glass (n = 1.50) at an angle of incidence of $$30^\circ. $$What is the angle of refraction inside the glass?

Accepted Answer

$$19.5^\circ$$

Question 3

Which of the following is NOT a way that light interacts with matter at an interface between two materials?

Accepted Answer

Diffusion

Question 4

A point source of light is placed in front of a plane mirror. Where will the virtual image appear relative to the mirror?

Accepted Answer

At the same distance behind the mirror as the object is in front

Question 5

A swimmer underwater looks up at the surface. If the index of refraction of water is 1.33 and air is 1.00, what is the critical angle for total internal reflection at the water-air boundary?

Accepted Answer

$$48.8^\circ$$

Question 6

Which of the following best explains why the sky appears blue?

Accepted Answer

Blue light is scattered more than red light by air molecules due to its shorter wavelength.

Question 7

A woman stands on a dock and looks down at a fish in the water. To her, the fish appears:

Accepted Answer

Closer to the surface than it actually is.

Question 8

A ray of light in glass (n = 1.50) strikes the glass-air boundary at an angle of $$50^\circ to $$the normal. Will any of the light refract into the air?

Accepted Answer

No, because the angle is greater than the critical angle for glass-air.

Question 9

Which of the following is a real-world application of total internal reflection?

Accepted Answer

Fiber optic communication cables

Question 10

A light ray passes from medium 1 into medium 2 and bends away from the normal. Which of the following must be true?

Accepted Answer

$$n_1$$ \u003e $$n_2$$

Question 11

A flashlight produces a bundle of parallel rays. Which type of light source does this best approximate?

Accepted Answer

A parallel-ray source

Question 12

A book is illuminated by a lamp. Why can you see the words on the page from any angle?

Accepted Answer

Diffuse reflection scatters light in all directions from the page.

Question 13

A ray of light in air strikes a glass surface at $$30^\circ to $$the normal. If the index of refraction of glass is 1.50, what is the speed of light in the glass?

Accepted Answer

$$2.00 	imes 10^8$ m/s

Question 14

Which of the following best describes a virtual image formed by a plane mirror?

Accepted Answer

It appears to be behind the mirror and cannot be projected onto a screen.

Question 15

A starfish is at the bottom of a lagoon 3.0 m deep. What is the diameter of the circle on the water’s surface inside which a person above can see the starfish? (Assume $$n_{water} = 1.33$$, $$n_{air} = 1.00)$$

Accepted Answer

$$7.8 m$$

Question 16

Which of the following is true about the law of reflection?

Accepted Answer

The angle of incidence equals the angle of reflection, both measured from the normal.

Question 17

A person stands in water and looks down at their feet, which are 0.60 m below the water surface. If the index of refraction of water is 1.33, how far below the surface do their feet appear to be?

Accepted Answer

$$0.45 m$$

Question 18

Which of the following is a correct application of Snell’s Law?

Accepted Answer

$$n_1$$ \sin \$$theta_1$$ = $$n_2$$ \sin \$$theta_2$$

Ray Optics: The Ray Model of Light, Reflection, and Refraction

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