A beam of light of wavelength 590 nm is focussed by a converging lens of diameter 10.0 cm at a distnce of 20 cm from it. find the diameter of he disc image formed.

Options

A. `5.76xx10^(-4)cm`
B. `7.51xx10^(-4)cm`
C. `8.72xx10^(-4)cm`
D. `9.80 xx10^(-4)cm`

Answer

A

Explanation

Given wavelength `lambda=590 nm =590xx10^(-9)m`
Diameter of lens `=10xx10^(-2)m`
`:.` Radius of lens `=5xx10^(-2)m`
Focal length of lens `=20xx10^(-2)m`
Now, the diameter of image disc
`D=2R=2(1.22(lambdaD)/b)=((1.22xx590xx10^(-9)xx20xx10^(-2))/(5xx10^(-2)))xx2`
`~=5.76xx10^(-4)cm`