A schematic of a Michelson interferometer, used for the measurement of refractive index of gas, is shown in the figure. The transparent chamber is filled with a gas of refractive index $n_{g}$, where $n_{g} \neq 1$, at atmospheric pressure. If a $532 \: \mathrm{nm}$ laser beam produces $30$ interference fringes on the screen, then the number of fringes produced by a $632.8$ nm laser beam will be _________ (rounded off to one decimal place).
Note: Assume that the effect of beamsplitter width is negligible. The setup is placed in air medium with refractive index equal to $1$.
