Tag: physics

The minimum amount of energy released in annihilation of electron-positron is.

A spherical drop of radius $10$ has absorbed $40$ electrons. The energy required to given an additional electron to it is.

Cathode rays enter an electric field normal to the field. Then their path in the electric field is :

When the energy of the incident radiation is increased by 20%, The kinetic energy of the photelectrons emitted from a metal surfce in creased from 0.5V to 0.8eV The work function of the metal is 

Out of the following transitions, the frequency of emitted photon will be maximum for 

When electron is incident on molybdenum they by changing energy of electron:-

An electron beam moving with a speed of $2.5\times 10^{7}ms^{-1}$  enters into the magnetic field directed perpendicular to its direction of motion. The magnetic induction of the field is $4\times 10^{-3}  wb/m^2$. The intensity of the electric field applied so that the electron remains undeflected due to the magnetic field is.

J.J. Thomson's cathode-ray tube experiment demonstrated that:

A particle of mass $1\times 10^{-26} \ kg $ and charge $1.6\times 10^{-19} \ C$ travelling with a velocity $1.28\times 10^6 \ m/s$ along the positive $X$-axis  enters a region in which a uniform electric field $\vec E$ and a uniform magnetic field of induction $\vec B$ are present. if $\vec E=-102.4 \times 10^3 \ \hat k \ NC^{-1}$ and $\vec B=8 \times 10^{-2} \ \hat j \ Wbm^{-2}$, the direction of motion of the particles is 

A proton and an $\alpha$ particle enter a magnetic field in a direction perpendicular to it. If the force acting on the proton is twice that acting on the $\alpha$- particle, the ratio of their velocities is