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Class 10
Solutions to CBSE Sample Paper - Science Class 10

Which diagram shows image formation of an object on a screen by a converging lens?

Q18 - screen by a converging lens - Teachoo.jpg

Answer - 

While drawing ray diagram , we follow these rules

  • A ray parallel to the principal axis will pass through the principal focus.
  • A ray passing through the principal focus will become parallel to the principal axis.
  • A ray passing through the optical center will emerge without deviation.

rule-1---ray-parallel-to-principal-axis-will-pass-through-focus-2---teachoo.jpg

rule-2---ray-passing-through-focus-will-become-parallel-to-principal-axis---teachoo.jpg

rule-3---ray-passing-through-optical-center-will-emerge-without-deviation---teachoo.jpg

 

In our diagram

Q18 - screen by a converging lens - Teachoo.jpg

  • In Option A : Converged ray passes through twice focal length, and not focal length. So, this is incorrect.
  • In Option B : Converged ray passes through twice focal length , and not focal length. So, this is incorrect.
  • In Option C : Converged ray passes through focal length, and ray passing through Optical center does not deviate. Thus, it follows all rules . So, Option C is correct .
  • In Option D: Ray passing through focus (bottom ray) will become parallel to principal axis , but here ray passing through focus again converges... which is incorrect. So, this is incorrect .

So, the correct answer is (c)  

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