Ray Optics

JEE Main level, numerical answer, medium

104 of 295

Question 104 of 295

A ray of light is incident at an angle of incidence 60∘60^{\circ} on the glass slab of refractive index 3\sqrt{3}. After refraction, the light ray emerges out from other parallel faces and lateral shift between incident ray and emergent ray is 43cm4\sqrt{3}cm. The thickness of the glass slab is _____ cmcm.

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Answer: 12


From snell's law,
sin⁡isin⁡r=3⇒sin⁡60∘sin⁡r=3⇒r=30∘\dfrac{\sin i}{\sin r}=\sqrt{3}\Rightarrow \dfrac{\sin 60^{\circ}}{\sin r}=\sqrt{3}\Rightarrow r=30^{\circ}
From the diagram shown,
d=tsin⁡(i−r)cos⁡r⇒t×1232=43⇒t=12cmd=\dfrac{t\sin \left(i-r\right)}{\cos r}\Rightarrow \dfrac{t\times \dfrac{1}{2}}{\dfrac{\sqrt{3}}{2}}=4\sqrt{3}\Rightarrow t=12cm

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