CBSE Class 12 · 2010 · Geometrical OpticsShort Answer

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(i) Out of blue and red light, which is deviated more by a prism? Give reason.
(ii) Give the formula that can be used to determine the refractive index of the material of a prism in the minimum deviation condition.

Solution

(i) Deviation

δ = (μ - 1) A

increases with

μ

. Blue light has a shorter wavelength and hence a \emph{larger} refractive index than red, so it is \emph{deviated more}.
(ii) In the minimum-deviation condition (with

A

the refracting angle and

δ_{m}

the angle of minimum deviation):

μ = \frac{sin ( \frac{A + δ _{m}}{2} )}{sin ( \frac{A}{2} )}

CBSE Class 12 Board · 2010 · Subjective

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