Dual Nature Of Radiation - Modern Physics - Physics Previous Year Questions

A beam of light of wavelength \(\lambda\) falls on a metal having work function \(\phi\) placed in a magnetic field B. The most energetic electrons, perpendicular to the field are bent in circular arcs of radius R. If the experiment is performed for different values of \(\lambda\), then \(\mathrm{B}^2\) vs. \(\frac{1}{\lambda}\) graph will look like (keeping all other quantities constant)

$10^{20}$ photons of wavelength 660 nm are emitted per second from a lamp. The wattage of the lamp is (Planck's constant $=6.6 \times 10^{-34} \mathrm{Js}$ )

An electron in Hydrogen atom jumps from the second Bohr orbit to the ground state and the difference between the energies of the two states is radiated in the form of a photon. This photon strikes a material. If the work function of the material is 4.2 eV , then the stopping potential is (Energy of electron in $n$-th orbit $\left.=-\frac{13 \cdot 6}{n^2} \mathrm{eV}\right)$

The de-Broglie wavelength of a moving bus with speed $v$ is $\lambda$. Some passengers left the bus at a stoppage. Now when the bus moves with twice of its initial speed, its kinetic energy is found to be twice of its initial value. What is the de-Broglie wavelength of the bus now?

When a beam of 10.6 eV photons of intensity $2.0 \mathrm{~W} / \mathrm{m}^2$ falls on a platinum surface of area $1.0 \times 10^{-4} \mathrm{~m}^2$ and work function $5.6 \mathrm{eV} .0 .53 \%$ of the incident photons eject photoelectrons. The number of photoelectrons emitted per second is

A parallel beam of fast moving electrons is incident normally on a narrow slit. If the speed of the electrons is decreased, the angular width of central maxima

Radiation of wavelength $\lambda$ is incident on a photocell．The fastest emitted electron has speed $v$ . If the wavelength is changed to $\frac{3 \lambda}{4}$ ，then the speed of the fastest emitted electron will be