The fundamental frequency of a sonometer wire is 50 Hz for some length and tension. If the length is increased by $25 \%$ by keeping tension same then frequency change of second harmonic is

In a single slit diffraction pattern, the distance between the plane of the slit and screen is 1.3 m . The width of the slit is 0.65 mm and the second maximum is formed at the distance of 2.6 mm from the centre of the screen. The wavelength of light used is

When source of sound and observer both are moving towards each other, the observer will hear

Water rises in a capillary tube of radius r upto ${ }^2$ height h . The mass of water in a capillary is m. The mass of water that will rise in capillary of radius $\frac{\mathrm{r}}{5}$ will be