Let $v$ be the frequency of the incident photon and $v_0$ be the threshold frequency. The condition for the emission of photoelectrons is:

When light of frequency $8 \times 10^{14} \ Hz$ is incident on a surface,photoelectrons are emitted with a maximum speed of $7 \times 10^5 \ m/s$. The threshold frequency for this surface is ..........

The threshold frequency of potassium is $3 \times 10^{14} \ Hz$. The work function is ...... .

The light of wavelength $\lambda$ is incident on the surface of a metal with work function $\phi$ and emits electrons. What is the maximum velocity of the emitted electrons? [Given: $m=$ mass of electron,$h=$ Planck's constant,$c=$ velocity of light]

Photoelectrons are emitted when photons of energy $4.2 \text{ eV}$ are incident on a photosensitive metallic sphere of radius $10 \text{ cm}$ and work function $2.4 \text{ eV}$. The number of photoelectrons emitted before the emission is stopped is
$\left[\frac{1}{4 \pi \epsilon_0}=9 \times 10^9 \text{ SI unit; } e=1.6 \times 10^{-19} \text{ C}\right]$

$A$ photon of energy $4 eV$ imparts all its energy to an electron that leaves a metal surface with $1.1 eV$ of kinetic energy. The work function of the metal is (in $eV$)