Page 149 - Physics_Form_2

Nature and reflection of light

Images formed by concave
mirrors A 1
The rules of reflection for concave Object 4
mirrors are used to locate an image 3 C 2 B F
formed by a concave mirror. These B P
rules are as follows: 2 4 A
FOR ONLINE READING ONLY
1. An incident ray that travels Image
parallel to the principal axis of
the mirror is reflected through 1
the focal point. Figure 4.24: Rays used to locate images
2. An incident ray that passes formed by concave mirrors
through the focal point is
reflected parallel to the principal In drawing ray diagrams, when the light rays
axis. diverge, they are extended backwards to locate

3. An incident ray that passes the image. In such cases, the image formed is
through the centre of curvature virtual because it is formed by virtual rays of
is reflected along its path. light, which are represented by dotted lines. The

4. An incident ray striking the image is real when it is formed by the intersection
pole of the mirror at an angle of real rays of light. Activity 4.8 assists on
to the principal axis is reflected experimental determination on behaviours of
such that the angle of incidence image formed by concave mirrors.
equals the angle of reflection,
measured with respect to the Activity 4.8
principal axis.
Aim: To determine the images formed
In Figure 4.24, the incident by concave mirrors
rays are drawn along with their Materials: graph paper, a sharp pencil, a ruler
corresponding reflected rays. Each
reflected ray converges at the image Procedure
location and then diverges to the eye 1. Choose an appropriate scale so that the ray
of an observer. Every observer can
observe the same image location, diagram fits on the available space.
and every light ray follows the 2. Draw a concave mirror at the centre of the
laws of reflection. However, only graph paper.
two of these rays are needed to 3. Draw a horizontal line passing through the
determine the image location since
it only requires two rays to find centre of the concave mirror. This is the
the intersection point. Figure 4.23 principal axis.
shows the rays used to locate images 4. Locate the centre of curvature and the focal
formed by concave mirrors. point on the principal axis. Choose the

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Physics Form 2 Final.indd 143 25/10/2025 10:27