In a certain double slit experimental arrangement interference fringes of width `1.0mm` each are observed when light of wavelength `5000Å` is used. Keeping the set up unaltered, if the source is replaced by another source of wavelength `6000Å`, the fringe width will be

Options

A. 1.2 mm
B. 1.5 mm
C. 1.8 mm
D. 2.0 mm

Answer

A

Explanation

Fringe width `beta=(lambdaD)/(d)`
As, `(beta_(1))/(beta_(2))=(lambda_(1))/(lambda_(2)) or (1)/(beta_(2))=(5000)/(6000)`
`rArr beta_(2)=(6000)/(5000)=1.2 mm `