Find the wavelength of electromagnetic radiation having frequency $1368 \ kHz$. (in $m$)

$A$ hypothetical electromagnetic wave is shown below. The frequency of the wave is $x \times 10^{19} \ Hz$. $x =$ . . . . (nearest integer)

Given below are two statements about $X$-ray spectra of elements :
Statement $(I) :$ $A$ plot of $\sqrt{\nu}$ ($\nu =$ frequency of $X$-rays emitted) vs atomic mass is a straight line.
Statement $(II) :$ $A$ plot of $\nu$ ($\nu =$ frequency of $X$-rays emitted) vs atomic number is a straight line.
In the light of the above statements choose the correct answer from the options given below :

Calculate the wavelength for the emission of a photon having a wave number of $11516 \ cm^{-1}$. (in $nm$)

The periodic time of radiation is $4 \times 10^{-10} \ s$. Find the wavelength,wave number,and frequency.

If the energies of two photons are in the ratio of $3:2$,their wavelengths will be in the ratio of