The focal length of thin convex lens for red and blue rays are $$100 \mathrm{~cm}$$ and $$98.01 \mathrm{~cm}$$, respectively. There, the dispersive power of the material of the lens is

If an object of height $$6 \mathrm{~cm}$$ is viewed through a liquid of refractive index $$\frac{4}{3}$$ vertically at a depth of $$10 \mathrm{~cm}$$. Then what will be its apparent height and apparent distance from the surface of liquid.

A plane glass mirror of thickness $$3 \mathrm{~cm}$$ of material of $$\mu=\frac{3}{2}$$ is silvered on the back surface. When a point object is placed $$9 \mathrm{~cm}$$ from the front surface of the mirror, then the position of the brightest image from the front surface is

An object is $$8 \mathrm{~cm}$$ high. It is desired to form a real image $$4 \mathrm{~cm}$$ high at $$60 \mathrm{~cm}$$ from the mirror. The type of mirror needed with the focal length is