If $f_{y}$ and $f_{b}$ are the focal lengths of a convex lens for yellow and blue colour respectively, then :

f_{y} = f_{b}

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f_{y} > f_{b}

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f_{y} < f_{b}

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\sqrt{f_{y}} = f_{b}

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Solution

The correct option is B $f_{y} > f_{b}$
Yellow has more wavelength than blue. So, deviation in yellow will be less. So, parallel beam of yellow light will converge at a large distance as compared to blue light convergence. So, focus for yellow light will be at larger distance from optical centre of lens. So, it has higher focal length.Hence $f_{y} > f_{b}$

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