Q. 5

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

A. The power of a converging lens.

B. The focal length of a converging lens.

C. The power of a diverging lens.

D. The focal length of a diverging lens.

Answer :

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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A thin prism of crown glass (μ_{r}=1.515, μ_{v} =1.525) and a thin prism of flint glass ((μ_{r}=1.612, μ_{v} =1.632) are placed in contact with each other. Their refracting angles are 5.0° each and are similarly directed. Calculate the angular dispersion produced by the combination.

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?

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HC Verma - Concepts of Physics Part 1Which of the following quantities increase when wavelength is increased? Consider only the magnitudes.

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