# An interference pattern is observed in a young 's double slit experiment in air. Now this chamber is evacuated and the same light is used we will see .

(a)no interference pattern

(b)interference with brighter bands

(c)interference with darker bands

(d)interference with fringe width slightly increased

We will see interference pattern with a slight increase in the fringe with $\beta$ as refractive index of vacuum is less then air.
$\beta_{air} =\large\frac{\Large \beta_ {vaccum}}{\mu _{air}}$
$\mu _{\Large air }$ slightly greater than 1
Hence d is the correct answer.