Q: The index of refraction $$n of a $$medium is defined as:

$$n = \frac{\text{speed of light in vacuum}}{\text{speed of light in medium}}$$

Q: What is the critical angle $$\theta_c$$ for total internal reflection at a water ($$n = 1.33) to $$air ($$n = 1.00) $$interface?

$$\theta_c = \arcsin\left(\frac{1.00}{1.33}\right) \approx 49^\circ$$

Question 1

A pencil is illuminated and observed using the ray model of light. Which statement best describes how the pencil is seen according to geometric optics?

Accepted Answer

Light rays travel in straight lines from the pencil to the eye, forming a bundle that enters the eye.

Question 2

A narrow beam of light strikes a flat mirror at an angle of incidence $$	heta_i = 30^\circ. $$What is the angle of reflection $$	heta_r$$?

Accepted Answer

$$	heta_r = 30^\circ$$

Question 3

Which of the following best describes diffuse reflection?

Accepted Answer

Light reflects from a rough surface, and the angle of reflection varies for different incident rays.

Question 4

A woman stands in front of a vertical plane mirror. If her height is $$1.60\ \mathrm{m}$$ and her eyes are $$0.10\ \mathrm{m}$$ below the top of her head, what is the minimum height of the mirror required for her to see her entire body?

Accepted Answer

$$0.80\ \mathrm{m}$$

Question 5

A concave spherical mirror has a radius of curvature $$r = 30.0\ \mathrm{cm}. $$What is its focal length $$f$$?

Accepted Answer

$$f = 15.0\ \mathrm{cm}$$

Question 6

Parallel rays of light strike a concave mirror with a small curvature. What happens to the rays after reflection?

Accepted Answer

They converge at the focal point of the mirror.

Question 7

An object is placed $$20.0\ \mathrm{cm}$$ from a concave mirror with a focal length of $$10.0\ \mathrm{cm}. $$Using the mirror equation $$\frac{1}{f} = \frac{1}{d_o} + \frac{1}{d_i}$$, what is the image distance $$d_i$$?

Accepted Answer

$$d_i = 20.0\ \mathrm{cm}$$

Question 8

A convex rearview mirror has a radius of curvature $$r = 16.0\ \mathrm{m}. $$What is its focal length $$f$$ and is it positive or negative?

Accepted Answer

$$f = -8.0\ \mathrm{m}$$

Question 9

The index of refraction $$n of a $$medium is defined as:

Accepted Answer

$$n = \frac{	ext{speed of light in vacuum}}{	ext{speed of light in medium}}$$

Question 10

A light ray passes from air ($$n_1 = 1.00$) into glass (n_2$ = 1.50) at an $$incident angle $$\$$theta_1$$ = 60.0^\circ. $$What is the angle of refraction $$\$$theta_2$$ in the glass according to Snell’s Law?

Accepted Answer

$$\$$theta_2$$ = 35.3^\circ$$

Question 11

What is the critical angle $$	heta_c$$ for total internal reflection at a water ($$n = 1.33) to $$air ($$n = 1.00) $$interface?

Accepted Answer

$$	heta_c = \arcsin\left(\frac{1.00}{1.33}ight) \approx 49^\circ$$

Question 12

Which statement about total internal reflection is correct?

Accepted Answer

It occurs when the angle of incidence exceeds the critical angle for the interface.

Question 13

A converging lens has a focal length $$f = 5.00\ \mathrm{cm}. $$What is its power $$P in $$diopters?

Accepted Answer

$$P = 20.0\ \mathrm{D}$$

Question 14

A $$7.6\ \mathrm{cm}$$ high leaf is placed $$1.00\ \mathrm{m}$$ from a converging lens with $$f = 5.00\ \mathrm{cm}. $$What is the magnification $$m of $$the image?

Accepted Answer

$$m = -0.0526$$

Question 15

A diverging lens has a focal length $$f = -25\ \mathrm{cm}. If a $$virtual image is to be formed $$20\ \mathrm{cm}$$ from the lens on the same side as the object, what is the object distance $$d_o$$?

Accepted Answer

$$d_o = 100\ \mathrm{cm}$$

Question 16

Which statement about the sign conventions for the thin lens equation is correct?

Accepted Answer

The image distance is positive if the image is on the opposite side from the light entering the lens.

Question 17

The lensmaker’s equation relates the focal length $$f of a $$lens to its radii of curvature $$R_1$$, $$R_2$$ and index of refraction $$n. $$Which is the correct form?

Accepted Answer

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

Question 18

In a compound lens system, the image formed by the first lens:

Accepted Answer

Becomes the object for the second lens.

Chapter 23: Light – Geometric Optics

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