Q: What is the critical angle for total internal reflection at a water-air interface? (Water: $$n_1 = 1.33$, Air: n_2$ = 1.0003$$; use $$\sin \theta_C = \frac{n_2$}{n_1$})$$

$$\theta_C \approx 48.8^\circ$$

Q: A plastic lens has a focal length of -0.5 m. What is its power and type?

$$P = -2 D$, \text{diverging lens}$$

Question 1

A beam of light passes from air (n = 1.0003) into water (n = 1.33) at an angle of incidence of 30°. What is the angle of refraction in the water? (Use Snell's Law: $$n_1$$ \sin \$$theta_1$$ = $$n_2$$ \sin \$$theta_2)$$

Accepted Answer

$$\$$theta_2$$ \approx 22.0^\circ$$

Question 2

Which of the following best explains why a straw appears bent when placed in a glass of water?

Accepted Answer

Refraction causes light to change direction as it passes from water to air.

Question 3

A diamond has an index of refraction of 2.42. What is the speed of light in diamond? (Use $$n = \frac{c}{v}$$, where $$c = 3.00 	imes 10^8$ m/s)

Accepted Answer

$$v = 1.24 	imes 10^8$ m/s

Question 4

What is the critical angle for total internal reflection at a water-air interface? (Water: $$n_1 = 1.33$, Air: n_2$ = 1.0003$$; use $$\sin 	heta_C = \frac{n_2$}{n_1$})$$

Accepted Answer

$$	heta_C \approx 48.8^\circ$$

Question 5

Which of the following is a practical application of total internal reflection?

Accepted Answer

Fiber optic communication cables

Question 6

A lens has a focal length of 0.25 m. What is its power in diopters?

Accepted Answer

$$P = 4.0 D$$

Question 7

A converging lens forms a real image of an object placed 30 cm from the lens. The image is formed 60 cm on the other side of the lens. What is the focal length of the lens? (Use $$\frac{1}{f} = \frac{1}{d_o} + \frac{1}{d_i})$$

Accepted Answer

$$f = 20 cm$$

Question 8

Which statement about the image formed by a diverging lens is correct?

Accepted Answer

The image is always upright and virtual.

Question 9

A ray of light passes from glass ($$n = 1.52) $$into air ($$n = 1.0003) at an $$angle of incidence of 45°. Will total internal reflection occur?

Accepted Answer

Yes, because the angle of incidence is greater than the critical angle.

Question 10

A lens produces an image with a magnification of $$m = -2. If $$the object height is 3 cm, what is the image height?

Accepted Answer

$$h_i = -6 cm$$

Question 11

Which material will slow down light the most, based on the indices of refraction provided?

Accepted Answer

Diamond

Question 12

A ray of light enters a glass slab ($$n = 1.52) $$from air at an angle of 60°. What is the angle of refraction inside the glass? (Use Snell's Law)

Accepted Answer

$$\$$theta_2$$ \approx 34.8^\circ$$

Question 13

Which of the following best describes the power of a lens?

Accepted Answer

It is the inverse of the focal length, measured in diopters.

Question 14

A fiber optic cable works primarily due to which optical phenomenon?

Accepted Answer

Total internal reflection

Question 15

If an object is placed at the focal point of a converging lens, what happens to the image?

Accepted Answer

The image is formed at infinity.

Question 16

A plastic lens has a focal length of -0.5 m. What is its power and type?

Accepted Answer

$$P = -2 D$, 	ext{diverging lens}$$

Question 17

Which ray tracing rule is correct for a thin lens?

Accepted Answer

A ray parallel to the axis passes through the focal point after refraction.

Question 18

A real image is formed by a lens when:

Accepted Answer

Light actually passes through the image location.

Question 19

A ray of light in water strikes the water-air interface at 60°. Will it undergo total internal reflection? (Water: $$n = 1.33$$, Air: $$n = 1.0003)$$

Accepted Answer

Yes, because 60° is greater than the critical angle.

Geometric Optics: Refraction, Total Internal Reflection, and Thin Lenses

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