The focal length of a convex lens is maximum | vedclass

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(D) The focal length $f$ of a lens is given by the Lens Maker's Formula: $\frac{1}{f} = (n - 1) \left( \frac{1}{R_1} - \frac{1}{R_2} \right)$.Accordin

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Red light

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(D) The focal length $f$ of a lens is given by the Lens Maker's Formula: $\frac{1}{f} = (n - 1) \left( \frac{1}{R_1} - \frac{1}{R_2} \right)$.According to Cauchy's equation,the refractive index $n$ of a material is higher for light of shorter wavelengths (like blue) and lower for light of longer wavelengths (like red).Since $n_{blue} > n_{red}$,the term $(n - 1)$ is larger for blue light than for red light.Because the focal length $f$ is inversely proportional to $(n - 1)$,a smaller value of $(n - 1)$ results in a larger focal length.Therefore,red light,having the longest wavelength and the smallest refractive index,results in the maximum focal length for a convex lens.

The focal length of a convex lens is maximum for which of the following?

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