The longest wavelength of light that can initiate the photoelectric effect in a metal with a work function of $9 \ eV$ is:

$A$ copper ball of radius $1\, cm$ and work function $4.47\, eV$ is irradiated with ultraviolet radiation of wavelength $2500\, \mathring{A}$. The effect of irradiation results in the emission of electrons from the ball. Further,the ball will acquire charge,and due to this,there will be a finite value of the potential on the ball. The charge acquired by the ball is:

Explain: "For photoelectric emission, the frequency of incident radiation should be greater than the threshold frequency."

The maximum velocity of the photoelectron emitted by the metal surface is $V$. The charge and mass of the photoelectron are denoted by $e$ and $m$ respectively. The stopping potential in volts is:

For a metal with a work function of $6.6 \text{eV}$, which of the following wavelengths of incident radiation does not cause the photoelectric effect (in $\text{nm}$)? (Take Planck's constant $h = 6.6 \times 10^{-34} \text{J s}$ and speed of light $c = 3 \times 10^8 \text{m/s}$)

Explain Einstein's photoelectric effect and derive Einstein's photoelectric equation.