A monoatomic gas does 100 J of work, when it is expanded isobarically. How much of heat is given to the gas in the process?

If the root mean square (rms) speed of nitrogen molecules at room temperature is $100 \mathrm{~m} / \mathrm{s}$, then the rms speed of helium molecule at the same temperature is

Two waves of amplitudes $A_1$ and $A_2$ respectively, are superimposed. The ratio between the maximum and minimum intensities of the resultant waves is $9: 4$.

The value of $\frac{A_2}{A_1}$ is (assume $A_1>A_2$ )

A lens is made of glass having an index of refraction 1.5 . One side of the lens is flat and the other side is convex with a radius $R$. If an object is placed 60 cm , towards the convex side of the lens, the image is formed at

120 cm on the other side of the lens. The value of $R$ is