Q: A converging lens has a focal length of $$10\ \text{cm}. An $$object is placed $$15\ \text{cm}$$ from the lens. Where is the image formed? (Use the thin lens equation: $$\frac{1}{f} = \frac{1}{d_o} + \frac{1}{d_i})$$

$$30\ \text{cm}$$ from the lens, on the opposite side

Q: A lens combination consists of two lenses: the first lens forms an image $$10\ \text{cm}$$ behind it, which becomes the object for the second lens placed $$20\ \text{cm}$$ away. What is the object distance for the second lens?

$$10\ \text{cm} ($$negative, since the image is on the same side as the incoming light)

Question 1

A person stands 2 meters in front of a plane mirror. How far behind the mirror does their image appear, and what type of image is formed?

Accepted Answer

2 meters; virtual image

Question 2

A ray of light strikes a flat mirror at an angle of incidence of $$30^\	ext{o}. $$What is the angle of reflection?

Accepted Answer

$$30^\	ext{o}$$

Question 3

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

Accepted Answer

Virtual, upright, and smaller

Question 4

A concave mirror has a radius of curvature of $$40\ 	ext{cm}. $$What is its focal length?

Accepted Answer

$$20\ 	ext{cm}$$

Question 5

A light ray passes from air ($$n_1 = 1.00$) into glass (n_2$ = 1.50) at an $$angle of incidence of $$30^\	ext{o}. $$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

$$19.5^\	ext{o}$$

Question 6

A fiber optic cable uses total internal reflection to transmit light. If the core has $$n_1 = 1.48$ and the cladding has n_2$ = 1.40$$, what is the critical angle for total internal reflection? (Use $$\sin 	heta_c = \frac{n_2$}{n_1$})$$

Accepted Answer

$$68.9^\	ext{o}$$

Question 7

A converging lens has a focal length of $$10\ 	ext{cm}. An $$object is placed $$15\ 	ext{cm}$$ from the lens. Where is the image formed? (Use the thin lens equation: $$\frac{1}{f} = \frac{1}{d_o} + \frac{1}{d_i})$$

Accepted Answer

$$30\ 	ext{cm}$$ from the lens, on the opposite side

Question 8

A diverging lens has a focal length of $$-20\ 	ext{cm}. An $$object is placed $$40\ 	ext{cm}$$ from the lens. What is the image distance? (Use $$\frac{1}{f} = \frac{1}{d_o} + \frac{1}{d_i})$$

Accepted Answer

$$-13.3\ 	ext{cm}$$

Question 9

Which scenario would result in total internal reflection?

Accepted Answer

Light passes from water ($$n=1.33) to $$air ($$n=1.00) at an $$angle greater than the critical angle

Question 10

A lens has a power of $$5\ 	ext{D} ($$diopters). What is its focal length?

Accepted Answer

$$0.2\ 	ext{m}$$

Question 11

A ray of light travels from water ($$n=1.33) $$into air ($$n=1.00) at an $$angle of incidence of $$60^\	ext{o}. $$Will total internal reflection occur?

Accepted Answer

Yes, because the angle is greater than the critical angle

Question 12

A concave mirror forms an image of an object placed between the focal point and the mirror. What are the characteristics of the image?

Accepted Answer

Upright, larger, and virtual

Question 13

A ray of light passes from glass ($$n=1.50) $$into water ($$n=1.33). If $$the angle of incidence is $$40^\	ext{o}$$, what is the angle of refraction? (Use Snell's law: $$n_1$$ \sin \$$theta_1$$ = $$n_2$$ \sin \$$theta_2)$$

Accepted Answer

$$45.7^\	ext{o}$$

Question 14

A lens combination consists of two lenses: the first lens forms an image $$10\ 	ext{cm}$$ behind it, which becomes the object for the second lens placed $$20\ 	ext{cm}$$ away. What is the object distance for the second lens?

Accepted Answer

$$10\ 	ext{cm} ($$negative, since the image is on the same side as the incoming light)

Question 15

Which of the following statements about the magnification produced by a mirror is correct?

Accepted Answer

Magnification is positive for upright images and negative for inverted images

Question 16

A ray of light passes through a thin lens parallel to the principal axis. After passing through a converging lens, where does the ray go?

Accepted Answer

It passes through the focal point on the opposite side

Question 17

Which equation relates the speed of light in a medium to its index of refraction?

Accepted Answer

$$n = \frac{c}{v}$$

Question 18

A lensmaker wants to design a lens with a focal length of $$25\ 	ext{cm}$$ using glass with $$n=1.52. If $$the radii of curvature are $$R_1 = 40$$\ 	ext{cm}$$ and R_2$ = -40\ 	ext{cm}$$, what equation should be used?

Accepted Answer

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

Question 19

A ray of light is incident on a rough surface. Which statement is true about the law of reflection?

Accepted Answer

The law of reflection applies, but the angle of incidence varies for each ray

Chapter 23

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