Electron Emission

A metal surface when exposed to ultraviolet radiations for a short interval of time was found to acquire${10}^{-9} \mathrm{C}$ positive charge. What happened to the metal surface?
 

The difference between threshold wavelengths for two metal surfaces $A$ and $B$ having work function ${\varphi }_A=9\mathrm{eV}$ and ${\varphi }_B=4.5\mathrm{eV}$ in $\mathrm{nm}$ is:

{Given, $hc=1242 \mathrm{eV} \mathrm{nm}$}

If radiation of energy $5 \mathrm{eV}$ is incident on the material with work function of $2.5 \mathrm{eV}$ then,

Will electrons eject when an incident ray of $3 \mathrm{kHz}$ is strike on a metal plate of threshold frequency $5 \mathrm{kHz}$.

When green light is incident on a certain metal surface, electrons are emitted but no electrons are emitted by yellow light. If red light is incident on the same metal surface

An isolated metal sphere is heated to a high temperature becomes positively charged.

What do you mean by thermionic emission?

Field electron emission is known as quick electron emissions.

A radiation of energy 'E' falls normally on a perfectly reflecting surface. The momentum transferred to the surface is (C = Velocity of light) :-

Assertion: An electric field is preferred in comparison to magnetic field for detecting the electron beam in a television picture tube.

Reason: Electric field require high voltage.

The dissociation energy of H₂ is 430.53 KJ mol^-1. If H₂ is dissociated by illumination with radiation of wavelength 253.7 nm, the fraction of the radiant energy which will be converted into kinetic energy is given by

When barium is irradiated by a light of $\lambda =400\mathrm{0 }\AA$, all the photo electrons emitted are bent in a circle of radius 50 cm by a magnetic field of flux density 5.26 x 10-6 T acting perpendicular to plane of emission of photo electrons. Then,

A point source of light is taken away from the experimental setup of photoelectric effect. For this situation, mark out the correct statement(s).

A surface irradiated with light of wavelength $480 \mathrm{nm}$ gives out electrons with maximum velocity $v \mathrm{m} {\mathrm{s}}^{-1}$, the cut off wavelength being $600 \mathrm{nm}$. The same surface would release electrons with maximum velocity of $2v \mathrm{m} {\mathrm{s}}^{-1}$, if it is irradiated by the light of wavelength