Geometrical Optics | Physics JEE previous year questions with Solutions

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Topic Question Set

Q 1 :
Given below are two statements:

Statement I: When the white light passed through a prism, the red light bends lesser than yellow and violet.

Statement II: The refractive indices are different for different wavelengths in dispersive medium.

In the light of the above statements, choose the correct answer from the options given below: [2024]

Statement I is false but Statement II is true
Statement I is true but Statement II is false
Both Statement I and Statement II are false
Both Statement I and Statement II are true

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(D) As $λ_{r e d} > λ_{y e l l o w} > λ_{v i o l e t}$

Light ray with longer wavelength bends less. So red has minimum wavelength so least bends.

Q 2 :
If the refractive index of the material of a prism is cot(A/2), where A is the angle of prism then the angle of minimum deviation will be [2024]

$π - 2 A$
$\frac{π}{2} - 2 A$
$π - A$
$\frac{π}{2} - A$

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(A) $\cos \frac{A}{2} = \sin (\frac{A + δ_{m i n}}{2})$

$\frac{A + δ_{m i n}}{2} = \frac{π}{2} - \frac{A}{2}$

$δ_{m i n} = π - 2 A$

Q 3 :
The refractive index of a prism with apex angle A is cot A/2. The angle of minimum deviation is [2024]

$δ_{m} = 180^{o} - 4 A$
$δ_{m} = 180^{o} - 3 A$
$δ_{m} = 180^{o} - 2 A$
$δ_{m} = 180^{o} - A$

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(C) $μ = \frac{\sin (\frac{A + δ_{m}}{2})}{\sin \frac{A}{2}}$

$\frac{\cos \frac{A}{2}}{\sin \frac{A}{2}} = \frac{\sin (\frac{A + δ_{m}}{2})}{\sin \frac{A}{2}}$

$\sin (\frac{π}{2} - \frac{A}{2}) = \sin (\frac{A + δ_{m}}{2})$

$\frac{π}{2} - \frac{A}{2} = \frac{A}{2} + \frac{δ_{m}}{2} \Rightarrow δ_{m} = π - 2 A$

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