Modern Physics PYQ — Page 16

A nucleus with mass number $184$ initially at rest emits an $\alpha -$particle. If the $Q$ value of the reaction is $5.5\mathrm{MeV},$ calculate the kinetic energy of the $\alpha -$ particle.

A particle of mass $9.1\times {10}^{-31}\mathrm{kg}$ travels in a medium with a speed of ${10}^{6}m{s}^{-1}$ and a photon of radiation of linear momentum ${10}^{-27}\mathrm{kg}m{s}^{-1}$ travels in a vacuum. The wavelength of the photon is ____ times the wavelength of the particle.

A particle of mass $m$ moves in a circular orbit in a central potential field $U(r)={U}_{0}{r}^{4}.$ If Bohr's quantization conditions are applied, radii of possible orbitals ${r}_{n}$ vary with ${n}^{\frac{1}{\alpha }}$, where $\alpha$ is _______ .

The wavelength of the photon emitted by a hydrogen atom when an electron makes a transition from $n=2$ to $n=1$ state is:

In the given figure, the energy levels of hydrogen atom have been shown along with some transitions marked $A,B,C,D$ and $E$. The transitions $A,B$ and $C$ respectively represent 

An electron moving with speed $v$ and a photon moving with speed $c$, have the same D-Broglie wavelength. The ratio of the kinetic energy of the electron to that of a photon is:

A moving proton and electron have the same de-Broglie wavelength. If $K$ and $P$ denote the $K.E.$ and momentum respectively. Then choose the correct option :

The recoil speed of a hydrogen atom after it emits a photon in going from $n=5$ state to $n=5$ state will be

Identify the logic operation carried out. 

The stopping potential for electrons emitted from a photosensitive surface illuminated by light of wavelength $491\mathrm{nm}$ is $0.710V.$ When the incident wavelength is changed to a new value, the stopping potential is $1.43V.$ The new wavelength is :

Consider a situation in which reverse biased current of a particular $P-N$ junction increases when it is exposed to a light of wavelength $\leq 621\mathrm{nm}.$ During this process, enhancement in carrier concentration takes place due to generation of hole-electron pairs. The value of band gap is nearly.

If ${V}_{A}$ and ${V}_{B}$ are the input voltages (either $5V$ or $0V$) and ${V}_{0}$ is the output voltage then the two gates represented in the following circuits $(A)$ and $(B)$ are : 

Consider two separate ideal gases of electrons and protons having same number of particles. The temperature of both the gases are same. The ratio of the uncertainty in determining the position of an electron to that of a proton is proportional to:

In connection with the circuit drawn below, the value of current flowing through $2k\Omega$ resistor is______$\times {10}^{-4}A.$ 

For extrinsic semiconductors; when doping level is increased;

The de Broglie wavelength of a proton and $\alpha$-particle are equal. The ratio of their velocities is

The first three spectral lines of $H$-atom in the Balmer series are given ${\lambda }_{1},{\lambda }_{2},{\lambda }_{3}$ considering the Bohr atomic model, the wave lengths of first and third spectral lines $(\frac{{\lambda }_{1}}{{\lambda }_{3}})$ are related by a factor of approximately $x$ $\times {10}^{-1}$. The value of $x$, to the nearest integer, is ________.

For the forward biased diode characteristics shown in the figure, the dynamic resistance at ${I}_{D}=3\mathrm{mA}$ will be ________$\Omega .$ 

An electron having de-Broglie wavelength $\lambda$ is incident on a target in a $X$-ray tube. Cut-off wavelength of emitted $X$-ray is:

In a given circuit diagram, a $5V$ zener diode along with a series resistance is connected across a $50V$ power supply. The minimum value of the resistance required, if the maximum zener current is $90\mathrm{mA}$ will be $\text{Ω.}$ 

The de-Broglie wavelength associated with an electron and a proton were calculated by accelerating them through same potential of $100V$. What should nearly be the ratio of their wavelengths $?$ $({m}_{p}=1.00727u,{m}_{e}=0.00055u)$

Which one of the following will be the output of the given circuit? 

Statement I: By doping silicon semiconductors with pentavalent material, the electrons density increases. Statement II: The $n-$type of semiconductor has a net negative charge. In the above statements, choose the most appropriate answer from the options given below:

A light beam of wavelength $500\mathrm{nm}$ is incident on a metal having work function of $1.25\mathrm{eV}$, 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 $30\mathrm{cm}$. The value of $B$ is ________$\times {10}^{-7}T$. Given $hc=20\times {10}^{-26}Jm$, the mass of the electron$=9\times {10}^{-31}\mathrm{kg}$.