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Question
Compare refraction in glass slab and in glass prism .
Compare refraction in glass slab and in glass prism .
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Solution
A glass slab causes apparent shift in the position of the because of refraction. The incident and the emergent rays are parallel but are displaced due to refraction causing apparent displacement of an object seen through a glass slab.
Deviation produced by a prism is due to the geometrical construction of the prism. Since the refracting sides are not parallel the deviations produced are more noticeable and also causes dispersion of light.
Glass Slab has parallel refracting surfaces whereas glass prism does not have parallel refracting surfaces.
The surfaces of a flat slab are parallel, so any refraction that takes place upon entering the slab is reversed upon leaving. Not so for the prism, the sides of which are at an angle.
When light enters the first surface of prism or a slab at an angle, the various frequencies refract at different angles. But since both surfaces of the slab are parallel, the refraction is reversed when the light leaves the slab: The various frequencies, while displaced a bit, leave the slab parallel. Not so for the prism: The different colors leave the prism at different angles, making it easy to see the dispersion.
In rectangular glass slab when the light Is refracted then, angle of incidence is equal to the angle of emergence.
1. Angle i = angle e > angle of refraction
2. Incident ray is parallel to the emergent ray.
But when light is refracted to the triangular glass prism then,
1. Angle i = angle e > angle of refraction.
2. Incident ray is not parallel to the emergent ray.
In the case of a glass slab, the two interfaces the light ray has to pass are parallel to each other. In this case the emergent ray is also a white light because the constituents of whitelight which are refracted at different angles at the first interface recombine at the second interface and emerge as a sigle white light.
In the case of a prism, the two interfaces the light ray has to pass are not parallel to each each other and are inclined at an angle. In this case, the effects of the first interface are not reversed and the colors separated at that first interface continue along different paths upon leaving the glass at the second interface. Hence we observe a spectrum on the other side.
Deviation produced by a prism is due to the geometrical construction of the prism. Since the refracting sides are not parallel the deviations produced are more noticeable and also causes dispersion of light.
Glass Slab has parallel refracting surfaces whereas glass prism does not have parallel refracting surfaces.
The surfaces of a flat slab are parallel, so any refraction that takes place upon entering the slab is reversed upon leaving. Not so for the prism, the sides of which are at an angle.
When light enters the first surface of prism or a slab at an angle, the various frequencies refract at different angles. But since both surfaces of the slab are parallel, the refraction is reversed when the light leaves the slab: The various frequencies, while displaced a bit, leave the slab parallel. Not so for the prism: The different colors leave the prism at different angles, making it easy to see the dispersion.
In rectangular glass slab when the light Is refracted then, angle of incidence is equal to the angle of emergence.
1. Angle i = angle e > angle of refraction
2. Incident ray is parallel to the emergent ray.
But when light is refracted to the triangular glass prism then,
1. Angle i = angle e > angle of refraction.
2. Incident ray is not parallel to the emergent ray.
In the case of a glass slab, the two interfaces the light ray has to pass are parallel to each other. In this case the emergent ray is also a white light because the constituents of whitelight which are refracted at different angles at the first interface recombine at the second interface and emerge as a sigle white light.
In the case of a prism, the two interfaces the light ray has to pass are not parallel to each each other and are inclined at an angle. In this case, the effects of the first interface are not reversed and the colors separated at that first interface continue along different paths upon leaving the glass at the second interface. Hence we observe a spectrum on the other side.
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