Q: A fiber optic cable transmits light using total internal reflection. Which condition must be met for total internal reflection to occur?

$$n_{core} \u003e n_{cladding}$$ \text{ and } \theta_{incidence} \u003e \theta_c$

Question 1

A light ray passes from air (n = 1.00) into glass (n = 1.50) at an angle of incidence of 30°. What is the angle of refraction in the glass? (Use Snell's Law: $$n_1$$ \sin \$$theta_1$$ = $$n_2$$ \sin \$$theta_2)$$

Accepted Answer

$$19.5^\circ$$

Question 2

Which of the following best describes why the sky appears blue during the day?

Accepted Answer

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

Question 3

A fish in a tank looks out through the flat side of the aquarium at a person standing outside. To the fish, the person appears to be:

Accepted Answer

Closer than the actual distance.

Question 4

A 3.0-cm-high object is placed 60 cm from a concave mirror with a focal length of 40 cm. Where is the image formed? (Use the mirror equation: $$\frac{1}{f} = \frac{1}{s} + \frac{1}{s'})$$

Accepted Answer

$$s' = 120\ \mathrm{cm}$$

Question 5

Which of the following statements about virtual images is correct?

Accepted Answer

A virtual image is a point from which rays appear to diverge, but no rays actually pass through it.

Question 6

A ray of light in water (n = 1.33) strikes the water-air interface at an angle greater than the critical angle. What happens to the ray?

Accepted Answer

It undergoes total internal reflection and remains in the water.

Question 7

A converging lens has a focal length of 10 cm. An object is placed 30 cm from the lens. Where is the image formed? (Use the thin-lens equation: $$\frac{1}{f} = \frac{1}{s} + \frac{1}{s'})$$

Accepted Answer

$$s' = 15\ \mathrm{cm}$$

Question 8

Which of the following is true about the image formed by a plane mirror?

Accepted Answer

The image is virtual and located the same distance behind the mirror as the object is in front.

Question 9

A magnifying glass with a focal length of 6 cm is held 4 cm from a flower. What is the magnification? (Use $$m = -\frac{s'}{s}$$ and the thin-lens equation.)

Accepted Answer

$$m = +3$$

Question 10

Which of the following best explains why a diverging lens cannot be used to start a fire with sunlight?

Accepted Answer

A diverging lens spreads parallel rays apart, so they cannot be focused to a point.

Question 11

A fiber optic cable transmits light using total internal reflection. Which condition must be met for total internal reflection to occur?

Accepted Answer

$$n_{core} \u003e n_{cladding}$$ 	ext{ and } 	heta_{incidence} \u003e 	heta_c$

Question 12

A 4.0-cm-diameter flower is 200 cm from a camera lens with a focal length of 50 cm. What is the diameter of the image on the detector? (Use magnification: $$m = -\frac{s'}{s}$$ and $$h' = m h)$$

Accepted Answer

$$1.3\ \mathrm{cm}$$

Question 13

A ray of light passes from glass (n = 1.50) into air (n = 1.00) at the critical angle. What is the angle of refraction?

Accepted Answer

$$90^\circ$$

Question 14

Which of the following is a correct statement about the law of reflection?

Accepted Answer

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

Question 15

A diverging lens with a focal length of -50 cm is placed 100 cm from a flower. Where is the image formed? (Use the thin-lens equation.)

Accepted Answer

$$s' = -33\ \mathrm{cm}$$

Question 16

A person stands in front of a plane mirror. What is the minimum height of the mirror required for the person to see their full image?

Accepted Answer

Half the person's height.

Question 17

A lens produces a sharply focused, inverted image on a screen. What will you see on the screen if the lens is removed?

Accepted Answer

No image at all.

Question 18

Which of the following best describes the image formed by a convex (diverging) mirror?

Accepted Answer

The image is always virtual, upright, and smaller than the object.

Question 19

A stamp collector uses a magnifying lens that sits 2.0 cm above the stamp. The magnification is 4. What is the focal length of the lens? (Use $$m = -\frac{s'}{s}$$ and the thin-lens equation.)

Accepted Answer

$$f = 2.7\ \mathrm{cm}$$

Chapter 18: Ray Optics – Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards