1.

The angle of a prism is A. One of its refracting surfaces is silvered. Light rays falling at an angle of incidence 2A on the first surface re turns back through the same path after suffer ing reflection at the silvered surface. The re fractive index m of the prism is

Answer»

2 sin A
2 COS A
`1/2` cos A
tan A

Solution :In `A=r_1+r_2,r_1=r` and `r_2=0 THEREFORE A=r`
From Snell.s law, `n_1sini=n_2sin r`
(1) sin2A=nsinA
`thereforen=(sin2A)/(sinA)`
`=(2sinAcosA)/(sinA)=2cosA`


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