CBSE Class 12-science Answered

Refractive index of the lens material, aμg =1.5

Focal length of the lens in air, fair = 15 cm

Using lens makers formula-

1/fair = (aμg-1) [1/R1 -1/R2]

1/15 = (1.5-1)[1/R1 -1/R2]

[1/R1 -1/R2] = 1/7.5

Refractive index of liquid, aμL =1.7

Refractive index of lens glass with respect to liquid, Lμg=aμg /aμL

 Lμg= 1.5/1.7 = 0.88

Let the focal length of the lens in liquid is-

1/fliquid = (Lμg-1)[1/R1 -1/R2]

1/fliquid = (0.88-1)[1/7.5]

= -0.015

So,fliquid = -66.67 cm.