The anode voltage of a photocell is kept constant. The wavelength of the light incident on the cathode is changed gradually. Which of the following graphs represents the variation of the photoelectric current $(I)$ with the wavelength $(\lambda)$?

The radiation corresponding to $3 \rightarrow 2$ transition of a hydrogen atom falls on a metal surface to produce photoelectrons. These electrons are made to enter a magnetic field of $3 \times 10^{-4} \ T$. If the radius of the largest circular path followed by these electrons is $10.0 \ mm$,the work function of the metal is close to......$ eV$.

When a light source of power $P$ emitting monochromatic light of wavelength $\lambda$ is kept at a distance $r$ from a photosensitive surface of work function $\phi$ and surface area $A$,which of the following is the wrong option?

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.

Photo cells are used for the:

The de Broglie wavelength of a particle moving with a speed of $0.8 c$ is equal to the wavelength of a photon. If $c$ is the speed of light in vacuum, the ratio of the energy of the photon to the kinetic energy of the particle is: