Assuming human pupil to have a radius of 0.25 cm and a comfortable viewing distance of 25 cm, the minimum separation between two objects than human eye can resolve at 500nm wavelength is :

Options

A. `1 mum`
B. `30mum`
C. `100 mum`
D. `300 mum`

Answer

B

Explanation

`D=2R=2xx0.25xx10^(-2)m`

Angular separation,
`d theta=(1.22lambda)/(D)`
`d theta=(1.22xx500xx10^(-9))/(2xx0.25xx10^(-2))`
`=(2440xx10^(-7))/(2)=1.22xx10^(-4)`
The distance of comfortable viewing is
`d=25cm=0.25m`
Minimum seperation
`x=d sin theta=d xx(d theta)`
`=0.25xx1.22xx10^(-4)=30mum`