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Explain refraction of plane wave with a thin prism. |
Answer» Solution : The figure shows the PARALLEL beam is incident on a prism at a instant and its correspondingplane wavefront `A_(1)B_(1). A_(1)B_(1)` is NORMAL to rays and emergent beam is shown by `A_(2)B_(2)`. Here the length of the path from `B_(1)` to `B_(2)` is greater then the length of the path from `A_(1)` to `A_(2)` In fact, the path from `A_(1)`to `A_(2)`in prism is larger than the path from `B._(2)` to `B._(2)` The VELOCITY of light in prism is less than the velocity in air hence it takes longer time for the light to go from `A_(1)` to `A_(2)` As a result, `A_(2)` is LAGGING behind point `B_(2)`. So the emergent wavefront is slightly tilted. |
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