Browse by Stream
QnA
Home
QnA
Go To Your Study Dashboard

Get Answers to all your Questions

header-bg qa
  • Home
  • School
  • a ) Define optical center of spherical lens  b) A divergent lens has a focal length of 20 cm. At what distance should an object be placed of height 4cm from the optical center of the lens, so that the image is formed 10cm away from the l

a ) Define optical center of spherical lens 

b) A divergent lens has a focal length of 20 cm. At what distance should an object be placed of height 4cm from the optical center of the lens, so that the image is formed 10cm away from the lens. Find the size of the image also.

c) Draw a ray diagram to show the formation of image in above situation 

 

 

 

 
 
 
 
 

Answers (1)

a)  Optical center is a point on the axis of a lens that is so located that any ray of light 

b)  focal length (f) = -20 cm 

Height of the object (h_1) = 4cm 

image distance (v) = -10 cm

object distance = ? 

sixe of the image (h_2) = ? 

According to the formula 

\frac{1}{f} = \frac{1}{v} - \frac{1}{u} \\\\ \frac{-1}{-10}- \frac{1}{-20}\\\\ = \frac{-1}{-10}+\frac{1}{20}\\\\ \frac{-2+1}{20}\\\\ \frac{-1}{20}\\\\u = -20 cm

so, the object is at distance of 20 can on the left side of lens 

Size of the image is given by 

h_2 = \frac{v}{u}h_1\\\\ = \frac{-10}{-20}\times 4 \\\\ = 2 cm

c) the ray diagram is given below 

Posted by

Priyanka Kumari

View full answer

Similar Questions

Trending Articles/News

anam-khan

CBSE sample papers 2024-25 for Class 10, 12 out at cbseacademic.nic.in; marking scheme
anam-khan

CBSE conducts surprise inspections at 27 schools in Rajasthan, Delhi to curb menace of dummy schools

Latest Question