Modern Physics — JEE Main PYQs

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 :

If ${\mathrm{M}}_{\mathrm{o}}$ is the mass of isotope ${}_5^{12}\mathrm{B}$, ${\mathrm{M}}_{\mathrm{p}}$ and ${\mathrm{M}}_{\mathrm{n}}$ are the masses of proton and neutron, then nuclear binding energy of isotope is :

A proton, an electron and an alpha particle have the same energies. Their de-Broglie wavelengths will be compared as:

A light emitting diode (LED) is fabricated using GaAs semiconducting material whose band gap is 1.42 eV. The wavelength of light emitted from the LED is:

The energy equivalent of 1 g of substance is:

A star has $100\%$ helium composition. It starts to convert three ${}^4\mathrm{He}$ into one ${}^{12}\mathrm{C}$ via triple alpha process as ${}^4\mathrm{He}+{}^4\mathrm{He}+{}^4\mathrm{He}\to {}^{12}\mathrm{C}+\mathrm{Q}$. The mass of the star is …

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

The de-Broglie wavelength associated with a particle of mass $m$ and energy $E$ is $\mathrm{h}/\sqrt{2mE}$. The dimensional formula for Planck's constant is :

UV light of 4.13 eV is incident on a photosensitive metal surface having work function 3.13 eV . The maximum kinetic energy of ejected photoelectrons will be :

The energy released in the fusion of 2 kg of hydrogen deep in the sun is ${\mathrm{E}}_{\mathrm{H}}$ and the energy released in the fission of 2 kg of ${}^{235}\mathrm{U}$ is ${\mathrm{E}}_{\mathrm{U}}$. The ratio $\frac{{\mathrm{E}}_{\mathrm{H}}}{{\mathrm{E}}_{\mathrm{U}}}$ is …

The atomic mass of ${}_6{\mathrm{C}}^{12}$ is 12.000000 u and that of ${}_6{\mathrm{C}}^{13}$ is 13.003354 u. The required energy to remove a neutron from ${}_6{\mathrm{C}}^{13}$, if mass of neutron is 1.008665 u, will be :

The threshold frequency of a metal with work function 6.63 eV is :

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

Two sources of light emit with a power of 200 W. The ratio of number of photons of visible light emitted by each source having wavelengths 300 nm and 500 nm respectively, will be :

Given below are two statements:

Statement I: Most of the mass of the atom and all its positive charge are concentrated in a tiny nucleus and the electrons revolve around it, is Rutherford's model.
Statement II: An atom is a spherical cloud of positive charges with electrons embe …

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 $\mathrm{T}=0\mathrm{K}$. The minimum potential difference needed to observe any Balmer series lines in th …

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

A convex lens of focal length 40 cm forms an image of an extended source of light on a photoelectric cell. A current I is produced. The lens is replaced by another convex lens having the same diameter but focal length 20 cm. The photoelectric current now is :

In a nuclear fission process, a high mass nuclide ($A\approx 236$) with binding energy $7.6\mathrm{MeV}/\mathrm{Nucleon}$ dissociated into middle mass nuclides ($A\approx 118$), having binding energy of $8.6\mathrm{MeV}/\mathrm{Nucleon}$. The energy released in the process wo …

The de-Broglie wavelength of an electron is the same as that of a photon. If velocity of electron is $25\%$ of the velocity of light, then the ratio of K.E. of electron and K.E. of photon will be:

The explosive in a Hydrogen bomb is a mixture of ${}_1{H}^2$, ${}_1{H}^3$ and ${}_{3}L{i}^6$ in some condensed form. The chain reaction is given by
${}_{3}L{i}^6{+}_0{n}^1{\to }_{2}H{e}^4{+}_1{H}^3$
${}_1{H}^2{+}_1{H}^3{\to }_{2}H{e}^4{+}_0{n}^1$
During the explosion the en …

When a hydrogen atom going from $n=2$ to $n=1$ emits a photon, its recoil speed is $\frac{X}{5}$ m/s. Where $x=$ ______. (Use : mass of hydrogen atom $=1.6\times 10^{-27}$ kg)

If the wavelength of the first member of Lyman series of hydrogen is $\lambda$. The wavelength of the second member will be

When a metal surface is illuminated by light of wavelength $\lambda$, the stopping potential is 8 V. When the same surface is illuminated by light of wavelength $3\lambda$, stopping potential is 2 V. The threshold wavelength for this surface is:

The mass defect in a particular reaction is 0.4 g.

The amount of energy liberated is $\mathrm{n}\times 10^7\mathrm{kWh}$, where $\mathrm{n}=$ ____.
$($ speed of light $=3\times 10^8\mathrm{m}/\mathrm{s})$

From the statements given below :
(A) The angular momentum of an electron in ${\mathrm{n}}^{\text{th }}$ orbit is an integral multiple of h .
(B) Nuclear forces do not obey inverse square law.
(C) Nuclear forces are spin dependent.
(D) Nuclear forces are central and charge indep …

Conductivity of a photodiode starts changing only if the wavelength of incident light is less than 660 nm . The band gap of photodiode is found to be $\left(\frac{\mathrm{X}}{8}\right)\mathrm{eV}$. The value of X is :
(Given, …

Monochromatic light of frequency $6\times 10^{14}\mathrm{Hz}$ is produced by a laser. The power emitted is $2\times 10^{-3}\mathrm{W}$. How many photons per second on an average, are emitted by the source ?
(Given $\mathrm{h}=6.63\times 10^{-34}\mathrm{Js}$ )

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

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:

The minimum energy required by a hydrogen atom in ground state to emit radiation in Balmer series is nearly :

The radius of a nucleus of mass number 64 is 4.8 fermi. Then the mass number of another nucleus having radius of 4 fermi is $\frac{1000}{x}$, where x is ______.

For the photoelectric effect, the maximum kinetic energy (${\mathrm{E}}_{\mathrm{k}}$) of the photoelectrons is plotted against the frequency (v) of the incident photons as shown in figure. The slope of the graph gives

In a nuclear fission reaction of an isotope of mass M, three similar daughter nuclei of same mass are formed. The speed of a daughter nuclei in terms of mass defect $\Delta \mathrm{M}$ will be:

An electron revolving in ${\mathrm{n}}^{\text{th }}$ Bohr orbit has magnetic moment ${\mu }_n$. If ${\mu }_n\alpha n^x$, the value of $x$ is:

The work function of a substance is 3.0 eV . The longest wavelength of light that can cause the emission of photoelectrons from this substance is approximately:

The ratio of the magnitude of the kinetic energy to the potential energy of an electron in the $5^{\text{th }}$ excited state of a hydrogen atom is :

A electron of hydrogen atom on an excited state is having energy ${\mathrm{E}}_{\mathrm{n}}=-0.85\mathrm{eV}$. The maximum number of allowed transitions to lower energy level is ____ . .

In a photoelectric effect experiment a light of frequency 1.5 times the threshold frequency is made to fall on the surface of photosensitive material. Now if the frequency is halved and intensity is doubled, the number of photo electrons emitted will be:

The mass number of nucleus having radius equal to half of the radius of nucleus with mass number 192 is:

A nucleus has mass number $A_1$ and volume $V_1$. Another nucleus has mass number $A_2$ and volume $V_2$. If relation between mass number is $A_2=4A_1$, then $\frac{V_2}{V_1}=$ ______.

A radio-active material is reduced to 1/8 of its original amount in 3 days. If $8\times 10^{-3}\mathrm{kg}$ of the material is left after 5 days. The initial amount of the material is

The waves emitted when a metal target is bombarded with high energy electrons are

In photo electric effect

A. The photocurrent is proportional to the intensity of the incident radiation.

B. Maximum Kinetic energy with which photoelectrons are emitted depends on the intensity of incident light.

C. Max. K.E with which photoelectrons are emitted depends on the …

The ratio of wavelength of spectral lines ${\mathrm{H}}_{\alpha }$ and ${\mathrm{H}}_{\beta }$ in the Balmer series is $\frac{\mathrm{x}}{20}$. The value of x is

For a nucleus ${}_{\mathrm{Z}}^{\mathrm{A}}\mathrm{X}$ having mass number A and atomic number Z

A. The surface energy per nucleon $\left(b_s\right)=a_1{A}^{2/3}$

B. The Coulomb contribution to the binding energy …

Proton (P) and electron (e) will have same deBroglie wavelength when the ratio of their momentum is (assume, ${\mathrm{m}}_{\mathrm{p}}=1849{\mathrm{m}}_{\mathrm{e}}$)

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

The work functions of Aluminium and Gold are 4.1 eV and 5.1 eV respectively. The ratio of the slope of the stopping potential versus frequency plot for Gold to that of Aluminium is

A small particle of mass $m$ moves in such a way that its potential energy $U=\frac{1}{2}m{\omega }^2{r}^2$ where $\omega$ is constant and $r$ is the distance of the particle from origin. Assuming Bohr's quantization of momentum and circular orbit, the radius of …