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

 

Answer  

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 .  

 

 

Student obtains a blurred image of a distant object.jpg

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)

  1. Class 10
  2. Chapter 10 Class 10 - Light - Reflection and Refraction (Term 1)

About the Author

CA Maninder Singh's photo - Founder at Teachoo
CA Maninder Singh
CA Maninder Singh is a Chartered Accountant for the past 11 years and a teacher from the past 11 years. He teaches Science, Accounts and English at Teachoo