The frequency of a radio station of All India Radio is $1368 \, kHz$. The wavelength of the electromagnetic waves emitted by the transmitter is ............... $m$.

Choose the correct statements in reference to the photoelectric effect. $(i)$ There is no time lag between the striking of light and ejection of electrons from the metal surface. $(ii)$ The number of electrons ejected is independent of the intensity of light. $(iii)$ The elements $K$, $Rb$ and $Cs$ can show photoelectric effect when exposed to the beam of light.

The blue colour of water in the sea is due to

Give the formulas for wave number and time period.

Explain line spectra and its uses.

Which of the following travels with the speed of light?