Lesson 3

use ray diagrams to describe an image formed by thin lenses and curved mirrors

1. If the angle between a plane mirror and an incident ray is 20 , then the angle between the incident ray and the reflected ray is:

a) 140

b) 90

c) 40

d) 20

2. When light goes from air into water, the

a) frequency increases

b) speed increases

c) frequency decreases

d) wavelength decreases

3. After light passes from air into a second medium, its speed is observed to be 2.0 x 108 m/s. The index of refraction

of the second medium is

a) 0.67

b) 1.3

c) 1.5

d) 6.0

4. Light with the longest wavelength is

a) yellow

b) violet

c) blue

d) red

Characteristic Description

magnification same size, enlarged or diminished

attitude erect or inverted

position displacement from mirror surface

type virtual or real

Concave mirrors curve away from the observer.

aka: converging mirror

Convex mirrors curve toward the observer.

aka diverging mirror

http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=48

VII - 17

Objects are drawn as erect arrows.

Real rays are solid lines

Virtual rays (only appear to exist behind the mirror) are dotted lines

VII - 19

• draw the mirror showing the principal axis, the centre of curvature, and the principal focal point

• place a vertical arrow on the principal axis to illustrate the position and size of the object

• draw two rays from the tip of the object arrow to the mirror

• draw the reflected rays from the mirror

• the point where the reflected rays meet (real image) or appear to diverge from (virtual image) is the position of the image

• draw a vertical arrow from the principal axis to the point mentioned above

Ans: hi = 6.1 cm, m = 0.72 inverted & smaller

A 8.5 cm candle is placed 13.6 cm from a concave mirror with focal length of 5.7 cm.

a) Find the distance the image is from the mirror.

Ans = 9.8 cm

b) Find the height of the image and the magnification factor.

b) Calculate the distance the image is away from the mirror.

Ans = 2.8 cm

c) Determine the image height.

Ans = 0.77 cm

Workbook p. 226-7 #1- 4 (mirror diagrams only)

Read text p. 656 - 662