A small angled prism is made of a material of refractive index $\frac{3}{2}$. The ratio of the angles of minimum deviations when the prism is placed in air and in water of refractive index $\frac{4}{3}$ is

If you are using eye glasses of power 2 D, your near point is

For a combination of two convex lenses of focal lengths $f_1$ and $f_2$ to act as a glass slab, the distance of separation between them is

If a ray of light passes through an equilateral prism such that the angle of incidence and the angle of emergence are both equal to $70 \%$ of the angle of the prism, then the angle of minimum deviation is