Which of the two has a greater power : a lens of short focal length or a lens of large focal length ?
Power is inversely proportional to the focal length. So a lens of short focal length has more power.
If lens I with focal length + 15 cm and lens II has focal length + 30 cm. find out which lens has more power?
An object of height 4.25 mm is placed at a distance of 10 cm from a convex lens of power +5 D. Find (i) focal length of the lens, and (ii) size of the image.
A converging lens has a focal length of 50 cm. The power of this lens is : (a) + 0.2 D (b) - 2.0 D (c) + 2.0 D (d) - 0.2 D
The power of a lens is + 0.2 D. Calculate its focal length.
Fill in the following blanks with suitable words : (a) The reciprocal of the focal length in metres gives you the of ___ the lens, which is measured in ___ (b) For converging lenses, the power is ___while for diverging lenses, the power is ___.
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 ?
A convex lens of focal length 25 cm and a concave lens of focal length 10 cm are placed in close contact with one another. (a) What is the power of this combination ? (b) What is the focal length of this combination ? (c) Is this combination converging or diverging ?