Modern Physics PYQ — Page 11

For a nucleus $XZA$ having mass number A and atomic number $Z$ A. The surface energy per nucleon$({b}_{s})=–{a}_{1}{A}^{\frac{2}{3}}.$ B. The Coulomb contribution to the binding energy ${b}_{c}=-{a}_{2}\frac{Z(Z-1)}{{A}^{\frac{4}{3}}}$. C. The volume energy ${b}_{v}={a}_{3}A$ D. Decrease in the binding energy is proportional to surface area. E. While estimating the surface energy, it is assumed that each nucleon interacts with 12 nucleons. (${a}_{1},{a}_{2}$ and ${a}_{3}$ are constants) Choose the most appropriate answer from the options given below:

An electron accelerated through a potential difference ${V}_{1}$ has a de-Broglie wavelength of $\lambda$. When the potential is changed to ${V}_{2}$, its de-Broglie wavelength increases by $50%$. The value of $(\frac{{V}_{1}}{{V}_{2}})$ is equal to :

If a source of electromagnetic radiation having power $15\mathrm{kW}$ produces ${10}^{16}$ photons per second, the radiation belongs to a part of spectrum is : (Take Planck constant $h=6\times {10}^{-34}Js)$

The ratio of de-Broglie wavelength of an $\alpha$-particle and a proton accelerated from rest by the same potential is $\frac{1}{\sqrt{m}}$ , the value of $m$ is:

The radius of ${2}^{\mathrm{nd}}$ orbit of ${\mathrm{He}}^{+}$ of Bohr's model is ${r}_{1}$ and that of fourth orbit of ${\mathrm{Be}}^{3+}$ is represented as ${r}_{2}.$ Now the ratio $\frac{{r}_{2}}{{r}_{1}}$ is $x:1.$ The value of $x$ is _____.

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R. Assertion A: Photodiodes are preferably operated in reverse bias condition for light intensity measurement. Reason R: The current in the forward bias is more than the current in the reverse bias for a $p-n$ junction diode. In the light of the above statement, choose the correct answer from the options given below :

The logic performed by the circuit shown in figure is equivalent to 

The output from a NAND gate having inputs A and B given below will be, 

A monochromatic light is incident on a hydrogen sample in ground state. Hydrogen atoms absorb a fraction of light and subsequently emit radiation of six different wavelengths. The frequency of incident light is $x\times {10}^{15}\mathrm{Hz}$. The value of x is ________ (Given $h=4.25\times {10}^{-15}\mathrm{eVs}$)

The angular momentum for the electron in Bohr’s orbit is $L$. If the electron is assumed to revolve in second orbit of hydrogen atom, then the change in angular momentum will be

A point source of light is placed at the centre of curvature of a hemispherical surface. The source emits a power of $24W$. The radius of curvature of hemisphere is $10\mathrm{cm}$ and the inner surface is completely reflecting. The force on the hemisphere due to the light falling on it is ______ $\times {10}^{-8}N$.

The mass of proton, neutron and helium nucleus are respectively $1.0073u,1.0087u\mathrm{and}4.0015u$. The binding energy of helium nucleus is:

The threshold frequency of metal is ${f}_{0}$. When the light of frequency $2{f}_{0}$ is incident on the metal plate, the maximum velocity of photoelectron is ${v}_{1}$. When the frequency of incident radiation is increased to $5{f}_{0}$. the maximum velocity of photoelectrons emitted is ${v}_{2}$. The ratio of ${v}_{1}$ to ${v}_{2}$ is:

A free neutron decays into a proton but a free proton does not decay into neutron. This is because

Which of the following statement is not correct in the case of light emitting diodes? A. It is a heavily doped p-n junction. B. It emits light only when it is forward biased. C. It emits light only when it is reverse biased. D. The energy of the light emitted is equal to or slightly less than the energy gap of the semiconductor used. Choose the correct answer from the options given below :

If the two metals $A$ and $B$ are exposed to radiation of wavelength $350\mathrm{nm}$. The work functions of metals $A$ and $B$ are $4.8\mathrm{eV}\text{and}2.2\mathrm{eV}$. Then choose the correct option

A $12.5\mathrm{eV}$ electron beam is used to bombard gaseous hydrogen at room temperature. The number of spectral lines emitted will be:

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

A metallic surface is illuminated with radiation of wavelength $\lambda$, the stopping potential is ${V}_{0}$. If the same surface is illuminated with radiation of wavelength $2\lambda$, the stopping potential becomes $\frac{{V}_{0}}{4}$. The threshold wavelength for this metallic surface will be

In photoelectric 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 frequency of incident light. D. The emission of photoelectrons require a minimum threshold intensity of incident radiation. E. Max K.E. of the photoelectrons is independent of the frequency of the incident light. Choose the correct answer from the options given below:

The energy levels of an atom is shown is figure.  Which one of these transitions will result in the emission of a photon of wavelength $124.1\mathrm{nm}$? Given ($h=6.62\times {10}^{–34}Js$)

The ratio of the de-Broglie wavelengths of proton and electron having same kinetic energy: (Assume ${m}_{p}={m}_{e}\times 1849$)

Statement I : When a Si sample is doped with Boron, it becomes P type and when doped by Arsenic it becomes N-type semi conductor such that P-type has excess holes and N-type has excess electrons. Statement II : When such P-type and N-type semi-conductors, are fused to make a junction, a current will automatically flow which can be detected with an externally connected ammeter. In the light of above statements, choose the most appropriate answer from the options given below.

A proton and an $\alpha$-particle are accelerated from rest by $2V$ and $4V$ potentials, respectively. The ratio of their de-Broglie wavelength is :