Q29 of 284 Page 262

What do you understand by the power of a lens ? Name one factor on which the power of a lens depend.

Power of lens is reciprocal of its focal length in metres.

P = 1/f


It depends on the focal length of the lens.


More from this chapter

All 284 →
27

The power of a combination of two lenses X and Y is S D. If the focal length of lens X be 1S cm :

(a) calculate the focal length of lens Y.


(b) state the nature of lens Y.

 28

Two lenses A and B have focal lengths of+ 20 cm and, -10 cm, respectively.

(a) What is the nature of lens A and lens B?


(b) What is the power of lens A and lens B?


(c) What is the power of combination if lenses A and B are held close together?

 29

What is the unit of power of a lens? Define the unit of power of a lens.

 29

A combination of lenses for a camera contains two converging lenses of focal lengths 20 cm and 40 cm and a diverging lens of focal length 50 cm. Find the power and focal length of the combination.