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Question : 7
Total: 27
Calculate the radius of curvature of a equiconcave lens of refractive index 1.5 , when it is kept in a medium of refractive index 1.4, to have a power of − 5 D
OR
An equilateral glass prism has a refractive index 1.6 in air. Calculate the angle of the minimum deviation of the prism, when kept in a medium of refractive index
OR
An equilateral glass prism has a refractive index 1.6 in air. Calculate the angle of the minimum deviation of the prism, when kept in a medium of refractive index
Solution:
Calculation of focal length
Lens maker's formula
Calculation of radius of curvature
f =
=
m = −
cm = − 20 cm
= (
− 1 ) (
−
)
µ 2 = 1.5 , µ 1 = 1.4 , R 1 = − R , R 2 = R
= (
− 1 ) ( −
−
)
= (
) ( −
)
R =
cm ( = 2.86 cm )
OR
Formula
Substitution and calculation
µ =
µ =
=
=
= √ 2
µ =
=
=
= √ 2
√ 2 =
=
∴ s i n (
) = √ 2 ⋅
=
= s i n 45 ∘
∴
= 45 ∘
∴ δ m = 30 ∘
Lens maker's formula
Calculation of radius of curvature
OR
Formula
Substitution and calculation
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