In producing a pure spectrum, the incident light is passed through a narrow slit placed in the focal plane of an achromatic lens because a narrow slit

By convention, the focal length of a concave mirror and a concave lens are taken as negative. Hence, both the spherical mirror and the thin spherical lens are concave in...

The power of a lens is related to its focal length as P = \(\frac{1}{f}\)(in m) More the power of a lens more is its converging power. Thus, the lens of shorter focal...

Hint — P = 1/f where f is in metre. Its unit is Dioptre. Lens is convex in the first case and concave in the second case. Power is equal...

Concave mirror and concave lens both have negative focal length, choice (c) is correct

Given P=+ 1.5D As P=1/f (in metre) , Focal length, f =1/P=1/1.5=0.667m=66.7cm As power of prescribed lens is positive, the lens is converging (or convex) lens.

P=1/f , P∝1/f. Power of a lens is inversely proportional to its focal length therefore lens having focal length of 20 cm will provide more convergence.

The correct answer is (c) 2 f EXPLANATION:  The intensity of the light on the other side is maximum where the image of the point source is formed.  Here u = -2f, f...

(b) The emergent beam is white. (c) The light inside the slab is split into different colours.

The illuminance will not change.

Power of a lens increases if red light is replaced by violet light because P = 1/f = (ang - 1)(1/R1 - 1/R2), and refractive index is maximum for violet light...