Aperture of human eye is 0.2cm. The minimum magnifying power of a visal telescope, whose objective has diameter100cm is.

Options

A. 500
B. 0.002
C. 2
D. 100

Answer

A

Explanation

Smallest angle that can be resolved by telescope is given by.
`d theta=(1.22lamda)/(D)`
Smallest angle that can be resolved by human eye is given by,
`d theta'=(1.22lamda)/(D_(e))`
Where `D_(e)` is the aperture of human eye, therefore the telescope must have a minimum magnifying power which must be such that, if an object substend an angle `d theta` its objective, then the final image produced must subtened an angle `d theta'` at the human eye.
`therefore` Minimum magnigyin power is given by
`,=(d theta')/(d theta)=(D)/(d_(e))`
`Rightarrow M=(100)/(0.2cm)=500`
`therefore D=100cm and D_(e)=0.2cm("given")`