Browse by Stream
QnA
Home
QnA
Go To Your Study Dashboard

Get Answers to all your Questions

header-bg qa
  • Home
  • NCERT
  • Double-convex lenses are to be manufactured from a glass of refractive index 1.55, with both faces of the same radius of curvature. What is the radius of curvature required if the focal length is to be 20cm?

Q 9.7  Double-convex lenses are to be manufactured from a glass of refractive index 1.55, with both faces of the same radius of curvature. What is the radius of curvature required if the focal length is to be 20cm?

Answers (1)

best_answer

As we know the lens makers formula 

\frac{1}{f}=(\mu _{21}-1)(\frac{1}{R_1}-\frac{1}{R_2}) 

 [ This is derived by considering the case when the object is at infinity and image is at the focus]

Where f = focal length of the lens

 \mu _{21} = refractive index of the glass of lens with the medium(here air)

  R_1 and R_2 are the  Radius of curvature of faces of the lens.         

Here, 

Given, f = 20cm,

          R_1  = R and R_2  =  -R

        \mu _{21} = 1.55

Putting these values in te equation,

\frac{1}{20}=(1.55-1)(\frac{1}{R}-\frac{1}{-R})

\frac{2}{R}=\frac{1}{20}*\frac{1}{0.55}

R = 40*0.55

R = 22cm

Hence Radius of curvature of the lens will be 22 cm.

Posted by

Pankaj Sanodiya

View full answer

Crack CUET with india's "Best Teachers"

  • HD Video Lectures
  • Unlimited Mock Tests
  • Faculty Support
cuet_ads

Similar Questions

Trending Articles/News

anam-khan

CBSE Class 12 Hindi exam 2025 not postponed; special exam for those who miss
anam-khan

CBSE Class 12 English Exam Analysis 2025: Paper rated 'easy, straightforward'; section-wise difficulty level
anam-khan

CBSE 12th Board Exam Live: CBSE Class 12 English paper 'easy and balanced'; answer key updates

Latest Question