Question

focal length of a lens is 20 cm then find its near point

Answer 1

Answer:

7.5 cm

Explanation:

According to figure, the point on the right side of the lens of which rays converge will behave as virtual object at the lens.

∴u=+12cm,f=20cm

By lens formula

1f=1v−1u

∴120=1v−112

or 1v=120+112=3+560=860

or u=608=7.5cm

So, image will be formed on same side of the virtual object at a distance of 7.5 cm from the lens.