Physics, asked by Rahulsunny7514, 1 year ago

A plano convex lens has a maximum thickness of 1mm. If diameter of aperture is 8cm then focal length

Answers

Answered by abhi178
0
see figure, here it is shown that A plano convex lens of thickness 1mm and diameter of its aperture is 8cm or 80mm. 

so, AB = radius of aperture = 40mm 
PC = radius of curvature = R 
then, BC = (R - 1) mm 
and AC = radius of curvature = R 

use Pythagoras theorem, 
AC² = AB² + BC² 
R² = 40² + (R - 1)² 
R² = 1600 + R² + 1 - 2R 
1601- 2R = 0
R = 800.5mm 
hence, R_1=R=800.5mm
and R_2=\infty [ because 2nd surface is plane ] 

now, use formula , \frac{1}{f}=(\mu-1)\left(\frac{1}{R_1}-\frac{1}{R_2}\right)

= (1.5 - 1) [ 1/800.5 - 1/∞ ] 

= 0.5/800.5 

= 1/1601

hence, f = 1601 mm or 160.1 cm
Attachments:
Similar questions