Question

i) Define power of a lens. Write its SI units.
(ii) You are provided with two convex lenses of focal length 15cm and 25cm respectively. Which of the two is of larger power? Give reason for your answer.
(iii) A 20cm tall object is placed perpendicular to the principal axis in front of a convex lens of focal length 10cm. The distance of the object from the lens is 15cm. Find the nature, position and size of the image. Also find its magnification.

Answer 1

Answer:

Explanation:

i)power of lens can be defined as the reciprocal of focal length

or another words the converging or diverging ability of lens.

ii)as power is inversely propotional to focal length this means more is the focal length less is the power of lens. Hence the power of 15 cm lens is more of the power of 25 cm lens.

iii) using mirror formula 1/v-1/u=1/f put the value

1/v-1/15=1/10 you can solve this ofcourse the answer will be v=6cm

as magnification in case of lens is V/U and Magnification (m) = h/h'

And h' is the image height and h is the object height. now the height of image will be 50cm

By solving v/u=h/h'