The photoelectric effect can be caused by which of the following?

Which of the following is $NOT$ a property of $X$-rays?

$750$ waves of an energy radiation pass in one minute from a point. What will be the wavelength of the radiation? (Assume the speed of radiation is $3 \times 10^8 \ m/s$)

When electromagnetic radiation of wavelength $300 \, nm$ falls on the surface of a metal, electrons are emitted with a kinetic energy of $1.68 \times 10^5 \, J \, mol^{-1}$. What is the minimum energy (work function) needed to remove one mole of electrons from the metal? $(h = 6.626 \times 10^{-34} \, J \, s, c = 3 \times 10^8 \, m \, s^{-1}, N_A = 6.022 \times 10^{23} \, mol^{-1})$

Electrons are emitted with zero velocity from a metal surface when it is exposed to radiation of wavelength $8000 \ \mathring{A}$. What should be the maximum velocity of emitted electron when the same metal surface is exposed to radiation of wavelength $5000 \ \mathring{A}$? $\left( h = 6.6 \times 10^{-34} \ J \cdot s, \ m_e = 9.1 \times 10^{-31} \ kg, \ c = 3 \times 10^8 \ m/s \right)$

$A$ photon-sensitive metal is not emitting photoelectrons when irradiated. It will do so when the threshold is crossed. To cross the threshold,we need to increase: