In Fresnel's biprism experiment, the source contains two wavelength 6000 Å and 5000 Å. The fourth order bright fringe of first wavelength is at a distance of 3 mm from the central band. The distance of the same order of bright band of second wavelength from the central band is

Options

A. 2.5 mm
B. 4.5 mm
C. 3.6 mm
D. 3 mm

Answer

A

Explanation

Distance of nth bright band from central band `x=(nDlamda)/(d)`
`implies(x_(1))/(x_(2))=(lamda_(1))/(lamda_(2))implies(3)/(x_(2))=(6000)/(5000)`
or `x_(2)=(3xx5)/(6)=2.5mm`.