What is the approximate radius of the central bright differaction spot of light of wavelength `lambda=0.5 mum`, if focal length of the lens is 20 cm and radius of aperture of the lens is 5 cm ?

Define focal length of a lens and calculate focal length of the lens having radius of curvature 30 cm.

The focal length of the lens in a photographic camera is 5cm. what is the power of the lens?

The focal length of the combination of two thin lenses in contact is 80 cm. If the focal length of one lens is -20 cm, what is the power of the other lens ?

A parallel beam of light falls on the surface of a convex lens whose radius of curvature of both sides of 20cm. The refractive index of the material of the lens varies as mu=1.5+0.5r , where r is the distance of the point on the aperture from the optical centre in cm. Find the length of the region on the axis of the lens where the light will appear. The radius of aperture of the lens is 1cm.

A parallel beam of light falls on the surface of a convex lens whose radius of curvature of both sides of 20cm. The refractive index of the material of the lens varies as mu=1.5+0.5r , where r is the distance of the point on the aperture from the optical centre in cm. Find the length of the region on the axis of the lens where the light will appear. The radius of aperture of the lens is 1cm.

Find the refractive index of the material of a plano-convex lens, if the radius of curvature of the convex surface is 20 cm and focal length of the lens is 60 cm?

Find the refractive index of the material of a plano-convex lens, if the radius of curvature of the convex surface is 20 cm and focal length of the lens is 60 cm?

If in a plano-convex lens radius of curvature of convex surface is 10 cm and the focal length of the lens is 30 cm, the refractive index of the material of the lens will be :