Modern Physics PYQ — Page 7

A hydrogen atom changes its state from $n=3$ to $n=2$. Due to recoil, the percentage change in the wave length of emitted light is approximately $1 \times 10^{-n}$. The value of $n$ is_____. [Given $\mathrm{Rhc}=13.6 \mathrm{eV}, \mathrm{hc}=1242 \mathrm{eV} \mathrm{nm}, \mathrm{h}=6.6 \times 10^{-34} \mathrm{~J} \mathrm{~s}$ mass of the hydrogenatom $=1.6 \times 10^{-27} \mathrm{~kg}$ ]

The disintegration energy $Q$ for the nuclear fission of ${ }^{235} \mathrm{U} \rightarrow{ }^{140} \mathrm{Ce}+{ }^{94} \mathrm{Zr}+n$ is ______ $\mathrm{MeV}$. Given atomic masses of ${ }^{235} \mathrm{U}: 235.0439 u ;{ }^{140} \mathrm{Ce}: 139.9054 u$, ${ }^{94} \mathrm{Zr}: 93.9063 u ; n: 1.0086 u \text {, }$ Value of $c^2=931 \mathrm{MeV} / \mathrm{u}$

The $I-V$ characteristics of an electronic device shown in the figure. The device is: 

Average force exerted on a non-reflecting surface at normal incidence is $2.4 \times 10^{-4} \mathrm{~N}$. If $360 \mathrm{~W} / \mathrm{cm}^2$ is the light energy flux during span of 1 hour 30 minutes, Then the area of the surface is:

If Rydberg's constant is $R$, the longest wavelength of radiation in Paschen series will be $\frac{\alpha }{7R}$, where $\alpha =$______.

Binding energy of a certain nucleus is $18 \times 10^8 \mathrm{~J}$. How much is the difference between total mass of all the nucleons and nuclear mass of the given nucleus:

Given below are two statements: one is labelled as Assertion $\mathbf{A}$ and the other is labelled as Reason R. Assertion A: Number of photons increases with increase in frequency of light. Reason R: Maximum kinetic energy of emitted electrons increases with the frequency of incident radiation. In the light of the above statements, choose the most appropriate answer from the options given below:

If the total energy transferred to a surface in time $t$ is $6.48\times {10}^{5}J$, then the magnitude of the total momentum delivered to this surface for complete absorption will be :

Radius of a certain orbit of hydrogen atom is $8.48 Ã…$. If energy of electron in this orbit is $E / x$. then $x=$ _____ (Given $\mathrm{a}_0=0.529 Ã…, E=$ energy of electron in ground state).

The de Broglie wavelengths of a proton and an $\alpha$ particle are $\lambda$ and $2\lambda$ respectively. The ratio of the velocities of proton and $\alpha$ particle will be :

Hydrogen atom is bombarded with electrons accelerated through a potential different of $V$, which causes excitation of hydrogen atoms. If the experiment is being formed at $T=0K$. The minimum potential difference needed to observe any Balmer series lines in the emission spectra will be $\frac{\alpha }{10}V$, where $\alpha =$_________.(Write the value to the nearest integer)

The explosive in a Hydrogen bomb is a mixture of $H21,H31$ and $\mathrm{Li}63$ in some condensed form. The chain reaction is given by $\mathrm{Li}63+n10\rightarrow \mathrm{He}42+H31$; $H21+H31\rightarrow \mathrm{He}42+n10$ During the explosion the energy released is approximately [Given : $M(\mathrm{Li})=6.01690\mathrm{amu},M(H21)=2.01471\mathrm{amu},M(\mathrm{He}42)=4.00388\mathrm{amu}$ and $1\mathrm{amu}=931.5\mathrm{MeV}$]

The angular momentum of an electron in a hydrogen atom is proportional to : (Where $r$ is the radius of orbit of electron)

The output $(Y)$ of logic circuit given below is 0 only when : 

The energy released in the fusion of $2 \mathrm{~kg}$ of hydrogen deep in the sun is $E_H$ and the energy released in the fission of $2 \mathrm{~kg}$ of ${ }^{235} \mathrm{U}$ is $E_U$. The ratio $\frac{E_H}{E_U}$ is approximately: (Consider the fusion reaction as $4 \mid H+2 \mathrm{e}^{-} \rightarrow{ }_2^4 \mathrm{He}+2 v+6 \gamma+26.7 \mathrm{MeV}$, energy released in the fission reaction of ${ }^{235} \mathrm{U}$ is $200 \mathrm{MeV}$ per fission nucleus and $\mathrm{N}_{\mathrm{A}}=$ $\left.6.023 \times 10^{23}\right)$

 In the truth table of the above circuit the value of $\mathrm{X}$ and $\mathrm{Y}$ are :

The atomic mass of $C126$ is $12.000000u$ and that of $C136$ is $13.003354u$. The required energy to remove a neutron from $C136$, if mass of neutron is $1.008665u$, will be:

A proton and an electron have the same de Broglie wavelength. If $\mathrm{K}_{\mathrm{p}}$ and $\mathrm{K}_{\mathrm{e}}$ be the kinetic energies of proton and electron respectively, then choose the correct relation :

The radius of third stationary orbit of electron for Bohr's atom is $R$. The radius of fourth stationary orbit will be:

Which of the following nuclear fragments corresponding to nuclear fission between neutron $\left({ }_0^1 \mathrm{n}\right)$ and uranium isotope $\left({ }_{92}^{235} \mathrm{U}\right)$ is correct :

A hydrogen atom in ground state is given an energy of $10.2 \mathrm{eV}$. How many spectral lines will be emitted due to transition of electrons?

A particular hydrogen - like ion emits the radiation of frequency $3\times {10}^{15}\mathrm{Hz}$ when it makes transition from $n=2$ to $n=1.$ The frequency of radiation emitted in transition from $n=3$ to $n=1$ is $\frac{x}{9}\times {10}^{15}\mathrm{Hz},$ when $x=$ _____.

Identify the logic gate given in the circuit: 

Identify the logic operation performed by the given circuit.