The spectrum of light emitted by a glowing solid is

$A$ light beam of wavelength $500 \, nm$ is incident on a metal having a work function of $1.25 \, eV$,placed in a magnetic field of intensity $B$. The electrons emitted perpendicular to the magnetic field $B$,with maximum kinetic energy,are bent into a circular arc of radius $30 \, cm$. The value of $B$ is $.... \times 10^{-7} \, T$.
Given $hc = 20 \times 10^{-26} \, J \cdot m$,mass of electron $m_e = 9 \times 10^{-31} \, kg$,and $e = 1.6 \times 10^{-19} \, C$.

The spectrum obtained from an electric lamp or a red-hot heater is:

Assertion: If the speed of a charged particle increases,both the mass and the charge increase.
Reason: If $m_0$ is the rest mass and $m$ is the mass at velocity $v$,then $m = \frac{m_0}{\sqrt{1 - \frac{v^2}{c^2}}}$,where $c$ is the speed of light.

Which microscope is used for nanotechnology?

$A$ photon and an electron have equal energy $E$. The ratio $\lambda_{\text{photon}} / \lambda_{\text{electron}}$ is proportional to: