Modern Physics PYQ — Page 12

The wavelength of the radiation emitted is ${\lambda }_{0}$ when an electron jumps from the second excited state to the first excited state of hydrogen atom. If the electron jumps from the third excited state to the second orbit of the hydrogen atom, the wavelength of the radiation emitted will be $\frac{20}{x}{\lambda }_{0}$. The value of $x$ is________.

The energy of ${\mathrm{He}}^{+}$ ion in its first state is, (The ground state energy for the Hydrogen atom$-13.6\mathrm{eV}$):

An electron of a hydrogen like atom, having $Z=4$, jumps from ${4}^{th}$ energy state to ${2}^{nd}$ energy state, The energy released in this process, will be: (Given $Rch=13.6eV$) Where $R=$ Rydberg constant $c=$Speed of light in vacuum $h=$ Planck's constant

For the given logic gates combination, the correct truth table will be 

The logic operations performed by the given digital circuit is equivalent to: 

Electron beam used in an electron microscope, when accelerated by a voltage of $20\mathrm{kV}$ has a de-Broglie wavelength of ${\lambda }_{0}$. If the voltage is increased to $40\mathrm{kV}$ then the de-Broglie wavelength associated with the electron beam would be:

The output waveform of the given logical circuit for the following inputs $A$ and $B$ as shown below, is 

The difference between threshold wavelengths for two metal surfaces $A$ and $B$ having work function ${\phi }_{A}=9\mathrm{eV}$ and ${\phi }_{B}=4.5\mathrm{eV}$ in $\mathrm{nm}$ is: {Given, $hc=1242\mathrm{eV}\mathrm{nm}$}

A small object at rest, absorbs a light pulse of power $20\mathrm{mW}$ and duration $300\mathrm{ns}$. Assuming speed of light as $3\times {10}^{8}m{s}^{-1}$. The momentum of the object becomes equal to :

For the following circuit and given inputs $A$ and $B,$ choose the correct option for output $‘Y’$  

The radius of fifth orbit of ${\mathrm{Li}}^{++}$ is$_______\times {10}^{-12}m.$ Take: radius of hydrogen atom$=0.51\overset{\circ }{A}$

Nucleus a having $Z=17$ and equal number of protons and neutrons has $1.2\mathrm{MeV}$ binding energy per nucleon. Another nucleus $B$ of $Z=12$ has total $26$ nucleons and $1.8\mathrm{MeV}$ binding energy per nucleons. The difference of binding energy of $B$ and $A$ will be ______ $\mathrm{MeV}$.

The de Broglie wavelength of a molecule in a gas at room temperature $(300K)$ is ${\lambda }_{1}$. If the temperature of the gas is increased to $600K$, then the de Broglie wavelength of the same gas molecule becomes

Speed of an electron in Bohr’s ${7}^{\mathrm{th}}$ orbit for Hydrogen atom is $3.6\times {10}^{6}m{s}^{-1}$. The corresponding speed of the electron in ${3}^{\mathrm{rd}}$ orbit, in $m{s}^{-1}$ is :

For hydrogen atom, ${\lambda }_{1}$ and ${\lambda }_{2}$ are the wavelengths corresponding to the transitions $1$ and $2$ respectively as shown in figure. The ratio of ${\lambda }_{1}$ and ${\lambda }_{2}$ is $\frac{x}{32}$. The value of $x$ is ______. 

A nucleus with mass number $242$ and binding energy per nucleon as $7.6\mathrm{MeV}$ breaks into two fragment each with mass number $121$. If each fragment nucleus has binding energy per nucleon as $8.1\mathrm{MeV},$ the total gain in binding energy is $_______\mathrm{MeV}$.

Match the List I with List II <table class="pyq-table"><tbody><tr><td></td><td>List I</td><td></td><td>List II</td></tr><tr><td>A</td><td>Intrinsic Semiconductor</td><td>I</td><td>Fermi-level near valence band</td></tr><tr><td>B</td><td>n-type semiconductor</td><td>II</td><td>Fermi-level at middle of valence and conduction band</td></tr><tr><td>C</td><td>p-type semiconductor</td><td>III</td><td>Fermi-level near conduction band</td></tr><tr><td>D</td><td>Metals</td><td>IV</td><td>Fermi-level inside conduction band</td></tr></tbody></table>Choose the correct answer from the options given below:

For the logic circuit shown, the output waveform at $Y$ is 

The effect of increase in temperature on the number of electrons in conduction band $({n}_{e})$ and resistance of a semiconductor will be as:

An $\alpha$ particle and a carbon $12$ atom has same kinetic energy $K$. The ratio of their de-Broglie wavelengths $({\lambda }_{\alpha }:{\lambda }_{C12})$ is

In hydrogen atom, the ratio of radii of first and second orbit is:

The de Broglie wavelength of a particle with momentum p is

The work function of a metal is 4.2 eV. The maximum kinetic energy of photoelectrons when light of wavelength 200 nm falls on it is:

Given below are two statements Statement I: In hydrogen atom, the frequency of radiation emitted when an electron jumps from lower energy orbit $({E}_{1})$ to higher energy orbit $({E}_{2})$, is given as $hf={E}_{1}-{E}_{2}$ Statement II: The jumping of electron from higher energy orbit $({E}_{2})$ to lower energy orbit $({E}_{1})$ is associated with frequency of radiation given as $f=\frac{({E}_{2}-{E}_{1})}{h}$. This condition is Bohr's frequency condition. In the light of the above statements, choose the correct answer from the options given below: