Page 171 - Physics_Form_2

Refraction and dispersion of light

overall deviation in the path of the light.
Incident ray Normal line This behaviour is illustrated in Figure 5.3.

i
Air Medium 1
FOR ONLINE READING ONLY
Glass Medium 2
r

Refracted ray

Figure 5.2: Light travelling from air to glass

Figure 5.3: Light refraction by a
Refraction of light by a glass prism rectangular glass block

Glass prisms come in various types,
including rectangular and triangular. Activity 5.2
Refraction occurs when light passes
through the prism, bending at the Aim: To investigate the refraction
interfaces due to changes in speed as it of light as it passes from air
enters and exits the glass. When light
enters the prism from air, it slows down to glass
and bends towards the normal line, which Materials: transparent glass block,
is perpendicular to the surface at the entry white piece of paper, a ray
point. Conversely, as light exits the prism box
back into the air, it speeds up and bends Procedure
away from the normal. 1. Place a transparent glass block on

a white piece of paper. Ensure that
Refraction of light by a rectangular the block is fixed so that it does not
prism move.
When a light ray passes from air into a 2. Place the ray box so that a ray of
rectangular glass prism, it undergoes light falls on the side of the block
refraction at the point where it enters the at a small angle to the normal as
glass. Inside the prism, the light travels in shown in Figure 5.4. Draw a line
a straight line until it reaches the opposite tracing the beam of light and mark
boundary, where it is refracted again as it the point at which light enters the
exits back into the air. Since the opposite glass block as M.
sides of a rectangular glass prism are 3. Mark the point at which the ray of
parallel, the emerging light ray continues light emerges from the other side of
in the same direction it had before the glass block as N and draw a line
entering the prism. As a result, there is no

165

Physics Form 2 Final.indd 165 25/10/2025 10:27