An astronaut is looking down on earth's surface from a space shuttle at an altitude of `400 km. ` Assuming that the astronaut's pupil diameter is `5 mm` and the wavelength of visible light is `500 nm. ` The astronaut will be able to resolve linear object of the size of about .

Options

A. 0.5m
B. 5m
C. 50m
D. 500m

Answer

C

Explanation

The resolving power of the eye is given by
`R=1.22 lamda/bxxD`
where `lamda` is the wavelength of light, b is the diameter of the eye lens and D is the distance from the lens at which light is focused.
`D=400km = 400000m, d=5mm = 5xx10^(-3)m`
`lamda = 500nm = 500xx10^(-9)m`
`therefore R=1.22xx(500xx10^(-9)xx4xx10^5)/(5xx10^(-3))=48.8~~50m`