The focal length of a lens is greatest for wh | vedclass

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(B) According to the lens maker's formula,$\frac{1}{f} = (\mu - 1) \left( \frac{1}{R_1} - \frac{1}{R_2} \right)$.Since the refractive index $\mu$ is i

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red

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(B) According to the lens maker's formula,$\frac{1}{f} = (\mu - 1) \left( \frac{1}{R_1} - \frac{1}{R_2} \right)$.Since the refractive index $\mu$ is inversely proportional to the wavelength $\lambda$ (Cauchy's equation: $\mu = A + \frac{B}{\lambda^2}$),the focal length $f$ is directly proportional to the wavelength $\lambda$.Red light has the longest wavelength in the visible spectrum.Therefore,the focal length of a lens is greatest for red light.

The focal length of a lens is greatest for which colour?

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