A convex lens is dipped in a liquid whose refractive index is equal to refractive index of lens material.…
A convex lens is dipped in a liquid whose refractive index is equal to refractive index of lens material. Then its focal length will
become infinite
remain same
decrease
become zero
Solution
Given that refractive of liquid is equal to refractive index of lens.
$\Rightarrow n_{\text {lens }}=n_{\text {liquid }}$
Let the focal length be $f$.
From lens makers formula, we get $\frac{1}{f}=\frac{\left(n_{\text {lens }}-n_{\text {liquid }}\right)}{n_{\text {liquid }}}\left(\frac{1}{R_1}-\frac{1}{R_2}\right)$
Here, $n_{\{\text {lens }\}}-n_{\{\text {liquid }\}}=0$
Therefore, the focal length will be infinite.