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# The refractive indices of flint glass for red and violet light are 1.613 and 1.632 respectively. Find the angular dispersion produced by a thin prism of flint glass having refracting angle $15 ^{\circ}$

Deviation of light $\delta = (\mu-1)A$
Deviation of Red light $\delta_{red} = (\mu_{red} - 1) A$ and that of the Violet light $\delta_{violet} = (\mu_{violet} - 1) A$
The dispersion $= \delta_{violet} - \delta_{red} = (\mu_{red} - 1) A - (\mu_{violet} - 1) A$
$\quad\quad = (\mu_{violet}-\mu_{red}) A$
$\quad\quad = (1.632-1.613) \times 15 ^{\circ}$
$\quad\quad = 0.285 ^{\circ}$