Modern Physics PYQ — Page 18

The radiation corresponding to $3\rightarrow 2$ 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 $7\mathrm{mm}$, the work function of the metal is: (Mass of electron $=9.1\times {10}^{-31}\mathrm{kg}$)

Statement I : To get a steady DC output from the pulsating voltage received from a full wave rectifier we can connect a capacitor across the output parallel to the load ${R}_{L}.$ Statement II : To get a steady DC output from the pulsating voltage received from a full wave rectifier we can connect an inductor in series with ${R}_{L}.$ In the light of the above statements, choose the most appropriate answer from the options given below :

The circuit contains two diodes each with a forward resistance of $50\Omega$ and with infinite reverse resistance. If the battery voltage is $6V$, the current through the $120\Omega$ resistance is _______ $\mathrm{mA}$

If an electron is moving in the ${n}^{\text{th }}$ orbit of the hydrogen atom, then its velocity $({v}_{n})$ for the ${n}^{\text{th }}$ orbit is given as:

The following logic gate is equivalent to : 

If ${\lambda }_{1}$ and ${\lambda }_{2}$ are the wavelengths of the third member of Lyman and first member of the Paschen series respectively, then the value of ${\lambda }_{1}:{\lambda }_{2}$ is :

An electron of mass $m$ and a photon have same energy $E.$ The ratio of wavelength of electron to that of photon is : ($c$ being the velocity of light)

The atomic hydrogen emits a line spectrum consisting of various series. Which series of hydrogen atomic spectra is lying in the visible region?

Imagine that the electron in a hydrogen atom is replaced by a muon $(\mu ).$ The mass of muon particle is $207$ times that of an electron and charge is equal to the charge of an electron. The ionization potential of this hydrogen atom will be:-

When radiation of wavelength $\lambda$ is incident on a metallic surface, the stopping potential of ejected photoelectrons is $4.8V$. If the same surface is illuminated by radiation of double the previous wavelength, then the stopping potential becomes $1.6V$. The threshold wavelength of the metal is:

Given below are two statements: Statement $I:$ Two photons having equal linear momenta have equal wavelengths. Statement $\mathrm{II}:$ If the wavelength of the photon is decreased, then the momentum and energy of a photon will also decrease. In the light of the above statements, choose the correct answer from the options given below.

The ${K}_{\alpha }$ X-ray of molybdenum has wavelength $0.071\mathrm{nm}$. If the energy of a molybdenum atom with a $K$ electron knocked out is $27.5\mathrm{keV}$, the energy of this atom when an $L$ electron is knocked out will be $\mathrm{keV}$. (Round off to the nearest integer ) $[h=4.14\times {10}^{-15}\mathrm{eV}s,c=3\times {10}^{8}{ms}^{-1}]$

In a semiconductor, the number density of intrinsic charge carriers at $27^{\circ}C$ is $1.5\times {10}^{16}{m}^{-3}$. If the semiconductor is doped with an impurity atom, the hole density increases to $4.5\times {10}^{22}{m}^{-3}$. The electron density in the doped semiconductor is _______$\times {10}^{9}{m}^{-3}$

A free electron of $2.6\mathrm{eV}$ energy collides with a ${H}^{+}$ ion. This results in the formation of a hydrogen atom in the first excited state and a photon is released. Find the frequency of the emitted photon. $(h=6.6\times {10}^{-34}Js)$

In the logic circuit shown in the figure, if input $A$ and $B$ are $0$ to $1$ respectively, the output at $Y$ would be $x$. The value of $x$ is _________. 

Four NOR gates are connected as shown in figure. The truth table for the given figure is : 

Find the truth table for the function $Y$ of $A$ and $B$ represented in the following figure. 

Two stream of photons, possessing energies equal to twice and ten times the work function of metal are incident on the metal surface successively. The value of ratio of maximum velocities of the photoelectrons emitted in the two respective cases is $x:3$ The value of $x$ is

An electron and proton are separated by a large distance. The electron starts approaching the proton with energy $3\mathrm{eV}$. The proton captures the electrons and forms a hydrogen atom in second excited state. The resulting photon is incident on a photosensitive metal of threshold wavelength $4000A$ What is the maximum kinetic energy of the emitted photoelectron?

Zener breakdown occurs in a $p-n$ junction having $p$and $n$ both:

A zener diode having zener voltage $8V$ and power dissipation rating of $0.5W$ is connected across a potential divider arranged with maximum potential drop across zener diode is as shown in the diagram. The value of protective resistance ${R}_{p}$ is _____$\Omega .$ 

An $\alpha$ particle and a proton are accelerated from rest by a potential difference of $200V$. After this, their de Broglie wavelengths are ${\lambda }_{\alpha }$ and ${\lambda }_{p}$ respectively. The ratio $\frac{{\lambda }_{p}}{{\lambda }_{\alpha }}$ is :

When radiation of wavelength $A$ is used to illuminate a metallic surface, the stopping potential is $V$. When the same surface is illuminated with radiation of wavelength $3A$, the stopping potential is $\frac{V}{4}$. If the threshold wavelength for the metallic surface is $n\lambda$ then value of $n$ will be :

The time period of revolution of electron in its ground state orbit in a hydrogen atom is $1.6\times {10}^{-16}s.$ The frequency of revolution of the electron in its first excited state (in ${s}^{-1}$ ) is: