OnlineCBT
Physics · PYQ NEET UG 2016(2)
हिन्दीTwo identical glass (\( \mu_3 = 3/2 \)) equiconvex lenses of focal length f each are kept in contact. The space between the two lenses is filled with water (\( \mu_w = 4/3 \)). The focal length of the combination is
Correct answer · Option B
\( \frac{f}{3} \)
Explanation
The combination acts as two equiconvex glass lenses and one liquid diverging lens in between. \( \frac{1}{F} = \frac{1}{f} + \frac{1}{f_{\text{liq}}} + \frac{1}{f} \). With \( f_{\text{liq}} = -\frac{f}{3} \), we get \( \frac{1}{F} = \frac{3}{f} \), so \( F = \frac{f}{3} \).
