# A prism having refractive index sqrt2 and refractive angle 30^@ has one of the refractive surfaces polished. A beam of light incident on the other

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A prism having refractive index sqrt2 and refractive angle 30^@ has one of the refractive surfaces polished. A beam of light incident on the other surfaces will trace its path if the angle of incidence is
A. 0^@
B. 30^@
C. 45^@
D. 60^@

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Correct Answer - C
If beam retraces its path, for this, ray must be incident normally on silvered surface.

1xxsini=musin30^@
sini=sqrt2xx1//2=1/sqrt2=sin45^@
i=45^@