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QJEEM24Phe242: JEE Main 2024 Physics - Class 12 JEEM24Phe242 Solution: A biconvex lens of refractive index 1.5 has a focal length of…

A biconvex lens of refractive index 1.5 has a focal length of 20 cm20 \mathrm{~cm} in air. Its focal length when immersed in a liquid of refractive index 1.6 will be:

Multiple Choice Options

  • A −- 16 cm
  • B +16 cm
  • C +160 cm
  • D −- 160 cm

Step-by-Step Verified Solution

amp;μ1=1.5amp;μm=1.6amp;fa=20 cmamp; As fmfa=(μ1−1)μm(μ1−μm)amp;fm20=(1.5−1)1.6(1.5−1.6)amp;fm=−160 cm\begin{aligned}& \mu_1=1.5 \\& \mu_m=1.6 \\& f_a=20 \mathrm{~cm} \\& \text { As } \frac{f_m}{f_a}=\frac{\left(\mu_1-1\right) \mu_m}{\left(\mu_1-\mu_m\right)} \\& \frac{f_m}{20}=\frac{(1.5-1) 1.6}{(1.5-1.6)} \\& f_m=-160 \mathrm{~cm}\end{aligned}

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