Page 143 - Physics_Form_2
P. 143
Nature and reflection of light
7. Measure and record the size mirror 1 and then off mirror 2 to your eyes
of the angles of incidence and (Figure 4.17). This third image is identical to
reflection. the other two except that it results from two
reflections, thus, it does not show right-left
Questions reversal. Image 3 is usually referred to as the
FOR ONLINE READING ONLY
(a) By what angle was the mirror secondary image. To explore the concept of
rotated? images formed by multiple mirrors, perform
(b) By what angle did the Activity 4.6.
reflected ray change its Mirror 1
direction? Object
Image 1
The reflected ray changes direction Eye
by an angle that is double the angle
through which the mirror is rotated. Mirror 2
Therefore, if the mirror is rotated by
an angle θ the reflected ray will rotate
by an angle 2θ. Image 3 Image 2
Multiple mirrors Figure 4.17: Multiple images in right-angle
Sometimes, systems are made up of mirrors
two or more mirrors and can create
multiple images of a single object. A Activity 4.6
common example of this is a right-
angle mirror. Aim: To determine the number of
images formed by multiple
Right-angle mirrors mirrors
Right-angle mirrors refer to two Materials: two plane mirrors, one object,
mirrors that are ‘joined’ at their four drawing pins, an optical
edges at an angle of 90°. Suppose board, protractor, ruler, plain
we take two mirrors and set them at paper
right angles to each other. You will Procedure
see a typical image in mirror 1 and 1. Using drawing pins, fix a plain paper on
another image in mirror 2. The two an optical board.
plane mirrors each produce a left-right
reversal of the images, that is, 1 and 2. 2. Draw two lines that are perpendicular
These images are sometimes referred (90) to each other on plain paper.
to as primary images. If you look 3. Place the two mirrors along the lines
carefully, you see that a third image 4. Place an object in front of the mirrors
is formed by the rays reflecting off as shown in Figure 4.18.
137
Physics Form 2 Final.indd 137 25/10/2025 10:27
