The diagram given below shows refraction of white light through a rectangular glass block.
(a) Name the two phenomena taking place at the surface AB.
(b) With a reason state whether one can see these colours when seen from the side DC.
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(a) The two phenomena taking place at the surface AB are :
- Refraction of light, and
- Dispersion of light.
(b) No, the separate colours cannot be seen when viewed from the side DC.
Reason — The two refracting surfaces AB and DC of a rectangular glass block are parallel to each other. At the first surface AB the colours get separated because each colour is deviated by a different amount. At the second surface DC, each colour is refracted in such a way that its emergent ray becomes parallel to the incident ray, so no further separation of colours takes place as it does in a prism. Hence the emergent coloured rays are parallel to one another and are so close together that they overlap, and the emergent light appears almost white.