Modern Physics — JEE Main PYQs

Given below are two statements : one is labelled as Assertion (A) and other is labelled as Reason (R).
Assertion (A) : Electromagnetic waves carry energy but not momentum.
Reason (R) : Mass of a photon is zero.
In the light of the above statements, choose the most appropriate ans …

The frequency of revolution of the electron in Bohr's orbit varies with n , the principal quantum number as

Which of the following phenomena can not be explained by wave theory of light ?

Choose the correct nuclear process from the below options
[p: proton, n: neutron, ${\mathrm{e}}^{-}$: electron, ${\mathrm{e}}^{+}$: positron, v: neutrino, $\bar{\nu }$: antineutrino]

A proton of mass '${\mathrm{m}}_{\mathrm{p}}$' has same energy as that of a photon of wavelength '$\lambda$'. If the proton is moving at non-relativistic speed, then ratio of its de Broglie wavelength to the wavelength of photon is. (Here $E$ denotes the common energy of the proton …

In photoelectric effect, the stopping potential ( ${\mathrm{V}}_0$ ) v/s frequency (v) curve is plotted.
( h is the Planck's constant and ${\varphi }_0$ is work function of metal)
(A) ${\mathrm{V}}_0\mathrm{v}/\mathrm{s}v$ is linear
(B) The slope of …

The energy E and momentum p of a moving body of mass $m$ are related by some equation. Given that c represents the speed of light, identify the correct equation.

The ratio of the power of a light source ${\mathrm{S}}_1$ to that the light source ${\mathrm{S}}_2$ is $2.{\mathrm{S}}_1$ is emitting $2\times 10^{15}$ photons per second at 600 nm . If the wavelength of the source ${\mathrm{S}}_2$ is 300 nm , then the number of photons per se …

During the transition of electron from state A to state C of a Bohr atom, the wavelength of emitted radiation is $2000\mathring{A}$ and it becomes $6000\mathring{A}$ when the electron jumps from state B to state C. Then the wavelength of the radiation emitted during the transition of electrons f …

An electron of mass ' m ' with an initial velocity $\overrightarrow{\mathrm{v}}={\mathrm{v}}_0\hat{\mathrm{i}}\left({\mathrm{v}}_0>0\right)$ enters an electric field $\overrightarrow{\mathrm{E}}=-{\mathrm{E}}_0\hat{\mathrm{k}}$. If the initial de Broglie wavelength is …

An electron with mass 'm' with an initial velocity $(t=0)\vec{v}=v_0\hat{i}$ $(v_0>0)$ enters a magnetic field $\vec{B}=B_0\hat{j}$. If the initial de-Broglie wavelength at $t=0$ is ${\lambda }_0$ then its value after time 't' would be :

Assuming the validity of Bohr's atomic model for hydrogen like ions the radius of $L{i}^{++}$ ion in its ground state is given by $\frac{1}{X}{a}_0$, where $X=$ ______.
(Where $a_0$ is the first Bohr's radius.)

Energy released when two deuterons ${(}_1{H}^2)$ fuse to form a helium nucleus (${}_{2}H{e}^4$) is :
(Given : Binding energy per nucleon of ${}_1{H}^2=1.1$ MeV and binding energy per nucleon of ${}_{2}H{e}^4=7.0$ MeV)

The work function of a metal is 3 eV . The color of the visible light that is required to cause emission of photoelectrons is

Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R.

Assertion A : The Bohr model is applicable to hydrogen and hydrogen-like atoms only.

Reason R : The formulation of Bohr model does not include repulsive force between electron …

An electron in the hydrogen atom initially in the fourth excited state makes a transition to $n^{\text{th}}$ energy state by emitting a photon of energy 2.86 eV. The integer value of n will be ____.

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R

Assertion A: In photoelectric effect, on increasing the intensity of incident light the stopping potential increases.

Reason R : Increase in intensity of light increases the rat …

Considering the Bohr model of hydrogen like atoms, the ratio of the ratio of the radius $5^{\text{th}}$ orbit of the electron in ${\text{Li}}^{2+}$ and ${\text{He}}^{+}$ is

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).

Assertion (A) : The density of the copper $\left({}_{29}^{64}\mathrm{Cu}\right)$ nucleus is greater than that of the carbon $\left({}_6^{12}\mathrm{C}\right)$ nuc …

A photo-emissive substance is illuminated with a radiation of wavelength ${\lambda }_{\mathrm{i}}$ so that it releases electrons with de-Broglie wavelength ${\lambda }_{\mathrm{e}}$. The longest wavelength of radiation that can emit photoelectron is ${\lambda }_0$. Expression for …

In a hydrogen like ion, the energy difference between the $2^{\text{nd}}$ excitation energy state and ground is 108.8 eV. The atomic number of the ion is

For a hydrogen atom, the ratio of the largest wavelength of Lyman series to that of the Balmer series is.

For a nucleus of mass number A and radius R, the mass density of nucleus can be represented as

An electron is released from rest near an infinite non-conducting sheet of uniform charge density '$-\sigma$'. The rate of change of de-Broglie wavelength associated with the electron varies inversely as ${\mathrm{n}}^{\text{th}}$ power of time. The numerical value of $n$ is ______ …

A radioactive material $P$ first decays into $Q$ and then Q decays to non-radioactive material R . Which of the following figure represents time dependent mass of $\mathrm{P},\mathrm{Q}$ and R ?

Given below are two statements :
Statement (I) : The dimensions of Planck's constant and angular momentum are same.
Statement (II) : In Bohr's model electron revolve around the nucleus only in those orbits for which angular momentum is integral multiple of Planck's constant.

In …

Considering Bohr's atomic model for hydrogen atom:
(A) the energy of H atom in ground state is same as energy of ${\mathrm{He}}^{+}$ ion in its first excited state.
(B) the energy of H atom in ground state is same as that for ${\mathrm{Li}}^{++}$ ion in its second excited state. …

A monochromatic light is incident on a metallic plate having work function $\varphi$. An electron, emitted normally to the plate from a point A with maximum kinetic energy, enters a constant magnetic field, perpendicular to the initial velocity of electron. The electron passes thr …

The longest wavelength associated with Paschen series is : (Given ${\mathrm{R}}_{\mathrm{H}}=1.097\times 10^7\mathrm{SI}$ unit)

When UV light of wavelength 300 nm is incident on the metal surface having work function 2.13 eV , electron emission takes place. The stopping potential is :\\
(Given hc $=1240\mathrm{eV}\mathrm{nm}$ )

In Franck-Hertz experiment, the first dip in the current-voltage graph for hydrogen is observed at 10.2 V. The wavelength of light emitted by hydrogen atom when excited to the first excitation level is ______ nm. (Given hc …

Given below are two statements : one is labelled as Assertion 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 …

According to Bohr's theory, the moment of momentum of an electron revolving in $4^{\text{th }}$ orbit of hydrogen atom is :

The disintegration energy $Q$ for the nuclear fission of ${}^{235}\mathrm{U}\to {}^{140}\mathrm{Ce}+{}^{94}\mathrm{Zr}+\mathrm{n}$ is ____ MeV.

Given atomic masses of
${}^{235}\mathrm{U}:235.0439\mathrm{u};{}^{140}\mathrm{Ce};139.9054\mathrm{u}$ …

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:

Which figure shows the correct variation of applied potential difference (V) with photoelectric current (I) at two different intensities of light ( ${\mathrm{I}}_1<{\mathrm{I}}_2$ ) of same wavelengths :

A hydrogen atom changes its state from $\mathrm{n}=3$ to $\mathrm{n}=2$. 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 Rhc $=13.6\mathrm{eV}$, hc …

Which of the following statement is not true about stopping potential ( ${\mathrm{V}}_0$ )?

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

The shortest wavelength of the spectral lines in the Lyman series of hydrogen spectrum is $915\text{A˚}$. The longest wavelength of spectral lines in the Balmer series will be ______ Å.

Given below are two statements:

Statement-I: Figure shows the variation of stopping potential with frequency ( $v$ ) for the two photosensitive materials ${\mathrm{M}}_1$ and ${\mathrm{M}}_2$. The slope gives value of $\frac{\mathrm{h}}{\mathrm{e}}$, where h is Planck's …

An electron rotates in a circle around a nucleus having positive charge Ze . Correct relation between total energy (E) of electron to its potential energy ( U ) is:

If three helium nuclei combine to form a carbon nucleus then the energy released in this reaction is ______ $\times 10^{-2}\mathrm{MeV}$. (Given $1\mathrm{u}=931\mathrm{MeV}/{\mathrm{c}}^2$, atomic mass of helium $=4.002603\mathrm{u}$)

The ratio of the shortest wavelength of Balmer series to the shortest wavelength of Lyman series for hydrogen atom is :

Which of the following phenomena does not explain by wave nature of light.
(A) reflection
(B) diffraction
(C) photoelectric effect
(D) interference
(E) polarization

Choose the most appropriate answer from the options given below :

In photoelectric experiment energy of 2.48 eV irradiates a photo sensitive material. The stopping potential was measured to be 0.5 V. Work function of the photo sensitive material is :

Radius of a certain orbit of hydrogen atom is $8.48\text{ A˚}$. If energy of electron in this orbit is $E/x$, then $x=$ ______.
(Given $a_0=0.529\text{ A˚}$, $E=$ energy of electron in ground state)

A proton and an electron are associated with same de-Broglie wavelength. The ratio of their kinetic energies is:
(Assume $\mathrm{h}=6.63\times 10^{-34}\mathrm{J}\mathrm{s},{\mathrm{m}}_{\mathrm{e}}=9.0\times 10^{-31}\mathrm{kg}$ and ${\mathrm{m}}_{\mathrm{p}}=1836$ tim …

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:

In a hypothetical fission reaction
${}_{92}{\mathrm{X}}^{236}\to {}_{56}{\mathrm{Y}}^{141}+{}_{36}{\mathrm{Z}}^{92}+3\mathrm{R}$
The identity of emitted particles ( R ) is :