A concave mirror is half dipped in water. Focal length of portion of mirror is the air is $f_1$ and focal length of mirror in water is $f_2$, then (Take refractive index of water $=\frac{4}{3}$)

Q. In the given figure, the focal length of the two mirrors $M-1$ and $M-2$ for the given incident rays are $f_1$ and $f_2$ respectively, then

Q. A thin convex lens made from crown glass $(\mu =\frac{3}{2})$ has focal length f. When it is measured in two different liquids having refractive indices $\frac{4}{3}and\frac{5}{3}$, it has the focal lengths $f_{1}and{f}_2$ respectively. The correct relation between the focal lengths is:

Q. To find the focal length of a convex mirror, a student records the following data:
The focal length of the convex lens is $f_1$ and that of mirror is $f_2$. Then taking index correction to be negligibly small, $f_1$ and $f_2$ are close to :

Q. Two thin lenses of focal lengths $f_1$ and $f_2$ are placed in contact with each other. The focal length of the combination will be given by: