A deviation of 2 ° is produced in the yellow ray when prism of crown… | JEE Main 2021 (16 Mar, Shift 2)

Q65JEE Main 2021 · 16 MAR · SHIFT 2Medium

Prism, Dispersion & Scattering

A deviation of 2 ${}^\circ$ is produced in the yellow ray when prism of crown and flint glass are achromatically combined. Taking dispersive powers of crown and flint glass as 0.02 and 0.03 respectively and refractive index for yellow light for these glasses are 1.5 and 1.6 respectively. The refracting angles for crown glass prism will be ____________ ${}^\circ$ (in degree). (Round off to the Nearest Integer)

Numerical answer type. Work it out, then open the answer.

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Answer: 12

Achromatic: $\omega_1(\mu_1 - 1)A_1 = \omega_2(\mu_2 - 1)A_2 \Rightarrow 0.02(0.5)A_1 = 0.03(0.6)A_2$ , so $A_2 = \dfrac{A_1}{1.8}$ .
Net deviation: $(\mu_1 - 1)A_1 - (\mu_2 - 1)A_2 = 2^\circ$ .
$0.5A_1 - 0.6\dfrac{A_1}{1.8} = \dfrac{A_1}{6} = 2^\circ$
$A_1 = 12^\circ$

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Prism, Dispersion & Scattering question from JEE Main 2021 (16 Mar, Shift 2)

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