An astronomical telescope has an eyepiece of focal-length 5cm. If the angular magnification in normal adjustment is 10, when final image is at least distance of distinct vision (25cm) from eye piece, then angular magnification will be :

Options

A. `10`
B. `12`
C. `50`
D. `60`

Answer

B

Explanation

For normal adjustment
`m=(f_(0))/(f_(e))`
When final image is at least distance of distinct vision from eyepiece,
`m'=-(f_(0))/(f_(e))(1+(f_(e))/(d))=10(1+(5)/(+25))=12`