Focal length of a convex lens of refractive index 1.5 is 2 cm . Focal length of lens when immersed i

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Focal length of a convex lens of refractive index 1.5 is 2 cm . Focal length of lens when immersed in a liquid of refractive index of 1.25 will be\

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(c) $: \frac{f_{a}}{f_{e}}=\frac{\left(\frac{\mu_{g}}{\mu_{l}}-1ight)}{\left(\mu_{g}-1ight)}=\frac{\left(\frac{1.5}{1.25}-1ight)}{1.5-1}=\frac{1 / 5}{1 / 2}=\frac{2}{5}$ $$ f_{e}=\frac{5}{2} f_{a}=\frac{5}{2} 	imes 2=5 \mathrm{~cm} $$