Two stars are situated at a distance of 8 light years from the earth. These are to be just resolved by a telescope of diameter 0.25 m. If the wavelength of light used is 5000 Å, then the distance between the stars must be

Options

A. `3xx10^(10)m`
B. `3.35xx10^(11)m`
C. `1.95xx10^(11)m`
D. `4.32xx10^(10)m`

Answer

C

Explanation

Limit of resolution of the telescope,
`alpha=(1.22lambda)/(a)=(d)/(x) rArr d=(1.22lambda x)/(a)`
`=(1.22xx5xx10^(-7)xx8xx10^(16))/(0.25)=1.95xx10^(11)m`