2. Questions Bank
  3. 10th Class
  4. Science
  5. Light - Reflection and Refraction

10th Class Science Light - Reflection and Refraction Question Bank Light - Reflection and Refraction

  • question_answer
    A converging lens magnifies a virtual image to four times its original size. Given that the focal length of the converging lens is 20 cm, what is the object distance?

    A) 5 cm                                     

    B) 10 cm                  

    C) 15 cm                                  

    D) 25 cm

    Correct Answer: C

    Solution :

    By using the lens equation, \[\frac{1}{u}+\frac{1}{v}=\frac{1}{f}\] \[\frac{1}{u}+\frac{1}{-4u}=\frac{1}{20}\to \frac{3}{4u}=\frac{1}{20},u=15\,cm\] Take note that a negative sign must be added to the image distance if the image is a virtual image.


You need to login to perform this action.
You will be redirected in 3 sec spinner