Ray Optics Test...

Dispersive power depends on the following

Two thin lenses of focal lengths f₁ and f₂ are placed in contact with each other. The focal length of the combination is

A convex lens is in contact with concave lens. The magnitude of the ratio of their focal length is 2/3. Their equivalent focal length is 30 cm. What are their individual focal lengths?

A thin glass (refractive index 1.5) lens has optical power of - 5 D in air. Its optical power in a liquid medium with refractive index 1.6 will be

Refractive index of glass with respect to medium is 4/3. If the differences between velocities of light in medium and glass is 6.25 × 10⁷ ms^-1, then velocity of light in medium is

The focal length of an equi-convex lens is greater than the radius of curvature of any of the surfaces. Then, the refractive index of the material of the lens is

An electric bulb of luminous intensity I is suspended at a height h from centre of the table having a circular surface diameter 2 r. The illuminance at centre of circular dis will be

At what distance should a book be placed from a 50 Cd bulb so that the illuminance on the book becomes 2 lmm^–2 ?

A point source of 100 candela is held 5m above a sheet of blotting paper which reflects 75% of light incident upon it. The illuminance of blotting paper is

Luminous flux and luminous intensity are related as