Page 191 - Physics_Form_2

Refraction and dispersion of light

when blue and green light enter the eye, a
cyan light is seen.

Task 5.3

Use a cardboard to make Newton’s
FOR ONLINE READING ONLY
colour wheel and observe the colours
as the wheel spins at different speeds.

Appearance of objects under white
light Figure 5.21: Coloured flowers
When one looks at an object, the object is
seen when it reflects light into the eye of White objects under coloured light
the observer. Objects may absorb certain An object is seen as white because it
colours of the light falling on them and reflects all colours of the white light
reflect other colours. Therefore, the falling on it. Therefore, when a white
colour appearance of objects depends object is viewed under the coloured light,
on the colour of the light that the object it will reflect the coloured light and hence
reflects or absorbs and the colour of the appear to have the colour of the light. For
light falling on the object. The selective example, when a white object is viewed
absorption or reflection of light by an under the blue light, it appears as a blue
object gives the object its characteristic object. Similarly, an object will appear
colour as perceived by an observer. red or green when viewed under red or
green light, respectively.

Coloured objects under white light
When white light falls on an object, Activity 5.9
and the object reflects the entire colour
spectrum in the light, the object appears Aim: To investigate the
appearance of a white
white. Conversely, the object appears object under coloured
black if it absorbs all colours of the white lights
light falling on it. If the object reflects
some of the colours and absorbs the Materials: colour filters (red, yellow,
others, the object appears coloured. For green and blue), a white
example, some flowers in Figure 5.21 object
appear yellow because they absorb all
other colours except the yellow colour, Procedure
which is reflected into the observer’s eyes. 1. Take filters of different colours
Other flowers also absorb all the colours (red, yellow, green and blue).
of white light except their respective 2. Let the light fall on the white object
colours, as seen in the Figure 5.21. through each colour filter.

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Physics Form 2 Final.indd 185 25/10/2025 10:28