Two glasses with refractive indices of `1.5 and 1.7` are used to make two indentical double convex lenses.
Find the ratio between their focal lengths.
How will each of these lenses act on a ray parallel to its optical axis if the lenses are submerged into a transparent liquid with a refractive index of `1.6?`

Answer

A, B, C, D

Explanation

(a) `1/f=(mu-1)(1/R_1-1/R_2)`
`:. fprop(1/(mu-1))`
or `f_1/(f_(2))=(mu_2-1)/(mu_1-1)=(1.7-1.0)/(1.5-1.0)=1.4`
(b) If refraction index of the liquid (or the medium)
is greater than the refraction index of
lens it changes its nature of converging lens
behaves as diverging.