Q5 of 27 Page 442

Which of the following quantities increase when wavelength is increased? Consider only the magnitudes.

Focal length of a lens is inversely proportional to the refractive index of a lens. Refractive index is also inversely proportional to the square of wavelength. Thus, we can conclude that the focal length is directly proportional to wavelength; it increases when the wavelength is increased.

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3

In producing a pure spectrum, the incident light is passed through a narrow slit placed in the focal plane of an achromatic lens because slit.

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Which of the following quantities related to a lens depend on the wavelength or wavelengths of the incident light?

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A flint glass prism and a crown glass prism are to be combined in such a way that the deviation of the mean ray is zero. The refractive index of flint and crown glasses for the mean ray are 1.620 and 1.518 respectively. If the refracting angle of the flint prism is 6.0°, what would be the refracting angle of the crown prism?

 2

A certain material has refractive indices 1.56, 1.60 and 1.68 for red, yellow and violet light respectively. A Calculate the dispersive power. B Find the angular dispersion produced by a thin prism of angle 6 made of this material.