An electromagnetic wave of wavelength $\lambda$ is incident on a photosensitive surface of negligible work function. If the photoelectrons emitted from this surface have the de-Broglie wavelength $\lambda_{1}$,then:

$A$ monochromatic light is incident on a metallic plate having work function $\phi$. An electron,emitted normally to the plate from a point $A$ with maximum kinetic energy,enters a constant magnetic field,perpendicular to the initial velocity of electron. The electron passes through a curve and hits back the plate at a point $B$. The distance between $A$ and $B$ is (Given: The magnitude of charge of an electron is $e$ and mass is $m$,$h$ is Planck's constant,and $c$ is velocity of light. Take the magnetic field exists throughout the path of electron).

In an experiment on the photoelectric effect,plates of three different metals $p, q,$ and $r$ are used,with work functions $\phi_p = 2.0\ eV$,$\phi_q = 2.5\ eV$,and $\phi_r = 3.0\ eV$,respectively. Three radiations of equal intensity with wavelengths $550\ nm, 450\ nm,$ and $350\ nm$ are incident on these plates. Which of the following $I \rightarrow V$ graphs is correct for the experimental results? $(hc = 1240\ eV\ nm)$

Photo cells are used for the:

The anode voltage of a photocell is kept fixed. The wavelength $\lambda$ of the light falling on the cathode is gradually changed. The plate current $I$ of the photocell varies as follows:

The radiation corresponding to the $3 \rightarrow 2$ transition of a hydrogen atom falls on a gold surface to generate photoelectrons. These electrons are passed through a magnetic field of $5 \times 10^{-4} \, T$. Assume that the radius of the largest circular path followed by these electrons is $7 \, mm$. The work function of the metal is $..... \, eV$. (Mass of electron $= 9.1 \times 10^{-31} \, kg$)