Question

A glass convex lens of refractive index 32 has got a focal length equal to 50cm Find the focal length of lens if it is immersed in ethyl alcohol of refractiveindex1.36

Answer 1

ANSWER

According to lens makers formula

1/f=(μ2μ1−1)[1R1−1R2]

1/f=(1.5−1)(1R1−1R2)

In ethyl alcohol

1t liquid=(1.51.36−1)[1R1−1R2]

So f liquid=(1.5−1)(1.5−11.36)×f

=242.75cm