If a gas has $n$ degrees of freedom, then the ratio of $\frac{C_p}{C_V}$ is

A bus moving with an uniform speed of $72 \mathrm{~km} / \mathrm{h}$ towards a building blows a horn of frequency 1.7 kHz . If speed of sound in air is $340 \mathrm{~m} / \mathrm{s}$, what will be the frequency of echo heard by bus driver?

If the image of an object is at the focal point $f$ to the right side of a convex lens, the position of the object on the left of the lens is at

On using red light $(\lambda=6600 \mathop {\rm{A}}\limits^{\rm{o}})$ in Young's double slit experiment, 60 fringes are observed in the field of view. If violet light ( $\lambda=4400 \mathop {\rm{A}}\limits^{\rm{o}}$ ) is used, the number of fringes observed will be