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If the angle of incidence and angle of e...

If the angle of incidence and angle of emergence of a light ray falling on a glass slab are i and e respectively, prove that, i = e.

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i. In the above figure,
i = angle of incidence,
r = angle of refraction,
e = angle of emergence.
At point N, using Snell's law,
`""_("glass")n_("air")=(sin i)/(sin r)" ….(1)"`
At point M, using Snell's law,
`""_("air")n_("glass")=(sin r)/(sin e)" ......(2)"`
But `""_("glass")n_("air")=(1)/(""_("air")n_("glass"))`
`therefore" "(sin i)/(sin r)=(1)/((sin r)/(sin e))" "`....[From (1) and (2)]
`therefore" "(sin i)/(sin r)=(sin e)/(sin r)`
`therefore" "sin i= sin e`
`therefore" "angle i = angle e`
ii. Hence, for the refraction of light through a glass slab angle of incidence is equal to angle of emergence, i.e., i=e.
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Knowledge Check

  • In the experiment on tracing the path of a ray of light passing through a rectangular glass slab, the correct setting of the protractor (D), for measuring the angle of incidence ( angle I ), and the angle of emergence ( angle e ) correspond, respectively, to diagrams :

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    `0^(@)`
    C
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    D
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  • A diverging beam of light from a point source S having devergence angle alpha , falls symmetrically on a glass slab as shown. The angles of incidence of the two extreme rays are equal. If the thickness of the glass slab is t and the refractive index n, then the divergence angle of the emergent beam is

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    zero
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