A student obtains a blurred image of a distant object on a screen using a convex lens. To obtain a distinct image on the screen he should move the lens
(a) away from the screen
(b) towards the screen
(c) to a position very far away from the screen
(d) either towards or away from the screen depending upon the position of the object
For a convex lens ,
- Since it is a distant object, it means object is at infinity
- Thus, image will be formed at focus
- Now, we don’t know where the screen is.
- The incident rays coming from the distant object will be parallel to the principal axis and as we know the rays parallel to the principal axis, after refraction by convex lens, will pass through the principal focus .
Hence, a distinct image will be obtained immediately when image distance (between screen and lens) is equal to focal length .
Since we don’t know where the screen is, we could either move towards or away from the screen depending upon the position of the object.
So, the correct answer is (d)