The kinetic energy of photoelectrons depends on ...............

What changes are observed in the color of iron as it is heated,and how does the frequency of the emitted radiation change?

Between a photon of violet light with a wavelength of $4000 \ \mathop A\limits^o$ and a photon of red light with a wavelength of $7000 \ \mathop A\limits^o$,which one has higher energy?

Consider a helium $(He)$ atom that absorbs a photon of wavelength $330 \ nm$. The change in the velocity (in $cm \ s^{-1}$) of the $He$ atom after the photon absorption is . . . . . .
(Assume: Momentum is conserved when the photon is absorbed. Use: Planck constant $= 6.6 \times 10^{-34} \ J \ s$,Avogadro number $= 6 \times 10^{23} \ mol^{-1}$,Molar mass of $He = 4 \ g \ mol^{-1}$)

The momentum (in $kg \cdot m/s$) of a photon having $6 \, MeV$ energy is:

Explain the production,characteristics,and uses of $X$-rays.