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Physics Question on Ray optics and optical instruments

A ray of light is travelling from glass to air. (Refractive index of glass = 1.51.5) The angle of incidence is 50∘50^\circ. The deviation of the ray is

A

Sin−1(Sin50∘1.5)−50∘Sin^{-1} \Big( \frac {Sin 50^\circ}{1.5} \Big)-50^\circ

B

50∘−Sin−1(Sin50∘1.5)50^{\circ}-Sin^{-1} \Big( \frac {Sin 50^{\circ}}{1.5} \Big)

C

80∘80^\circ

D

0∘0^\circ

Answer

80∘80^\circ

Explanation

Solution

Refractive index, aμg=1.5^{a} \mu_{g}=1.5
1sin⁡C=1.5\frac{1}{\sin C} =1.5
⇒C=42∘\Rightarrow C =42^{\circ}
Critical angle for glass =42∘=42^{\circ}
When the angle of incidence in the denser medium is greater than the critical angle, reflection takes place inside the denser medium.

Hence, a ray of light incident at 50∘50^{\circ} in glass medium undergoes total internal reflection. Deviation (δ)=180∘−(50∘+50∘)(\delta)=180^{\circ}-\left(50^{\circ}+50^{\circ}\right)
(from the-figure)
or δ=80∘\delta=80^{\circ}