# Angular width of Refracted Beam!

Classical Mechanics Level 4

A beam of light has a small wavelength spread $$\delta \lambda$$ about a central wavelength $$\lambda$$. The beam travels in vacuum until it enters a glass plate at an angle $$\theta$$ relative to the normal to the plate, as shown in the figure. The index of refraction of the glass is given by $$n(\lambda)$$. The angular spread $$\delta \theta '$$ of the refracted beam is given by?

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