Modern Physics PYQ — Page 9

Identify the logic operation performed by the given circuit. 

In the given circuit if the power rating of Zener diode is $10\mathrm{mW}$, the value of series resistance ${R}_{s}$ to regulate the input unregulated supply is: 

The value of net resistance of the network as shown in the given figure is : 

Conductivity of a photodiode starts changing only if the wavelength of incident light is less than $660\mathrm{nm}.$ The band gap of photodiode is found to be $(\frac{X}{8})\mathrm{eV}.$ The value of $X$ is: (Given $h=6.6\times {10}^{-34}Js,e=1.6\times {10}^{-19}C$)

The output of the given circuit diagram is 

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

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

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 $\Delta M$ will be :

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 output $\mathrm{Y}$ of following circuit for given inputs is : 

The mass defect in a particular reaction is $0.4g$. The amount of energy liberated is $n\times {10}^{7}\mathrm{kW}h$, where $n=$ _____. (speed of light $=3\times {10}^{8}m{s}^{-1}$)

When a hydrogen atom going from $n=2$ to $n=1$ emits a photon, its recoil speed is $\frac{x}{5}m{s}^{-1}$. Where $x=$_______. (Use: mass of hydrogen atom $=1.6\times {10}^{-27}\mathrm{kg}$, charge of electron $e=1.6\times {10}^{-19}C)$

Assume that protons and neutrons have equal masses. Mass of a nucleon is $1.6\times {10}^{-27}\mathrm{kg}$ and radius of nucleus is $1.5\times {10}^{-15}{A}^{\frac{1}{3}}m$. The approximate ratio of the nuclear density and water density is $n\times {10}^{13}$. The value of $n$ is _____.

As per given figure $A,B$ and $C$ are the first, second and third excited energy levels of hydrogen atom respectively. If the ratio of the two wavelengths$(i.e.\frac{{\lambda }_{1}}{{\lambda }_{2}})$ is $\frac{7}{4n}$, then the value of $n$ will be 

The work function of a metal is 4.2 eV. The threshold wavelength is (hc = 1240 eV·nm):

In Bohrs model the ratio of the kinetic energy to the total energy of the electron in nth orbit is:

An $\alpha$ particle, a proton and an electron have the same kinetic energy. Which one of the following is correct in case of their de-Broglie wavelength:

An atom absorbs a photon of wavelength $500\mathrm{nm}$ and emits another photon of wavelength $600\mathrm{nm}$. The net energy absorbed by the atom in this process is $n\times {10}^{-4}\mathrm{eV}$. The value of$n$is [Assume the atom to be stationary during the absorption and emission process] (Take $h=6.6\times {10}^{-34}Js$ and c=3\times 108 m s-1 ).

Given below are two statements : Statement I : Stopping potential in photoelectric effect does not depend on the power of the light source. Statement II : For a given metal, the maximum kinetic energy of the photoelectron depends on the wavelength of the incident light. In the light of above statements, choose the most appropriate answer from the options given below.

The energy levels of an hydrogen atom are shown below. The transition corresponding to emission of shortest wavelength is 

The threshold wavelength for photoelectric emission from a material is $5500\overset{\circ }{A}$. Photoelectrons will be emitted, when this material is illuminated with monochromatic radiation from a A. $75W$ infra-red lamp B. $10W$ infra-red lamp C. $75W$ ultra-violet lamp D. $10W$ ultra-violet lamp Choose the correct answer from the options given below :

The logic gate equivalent to the given circuit diagram is : 

The energy released per fission of nucleus of $X240$ is $200\mathrm{MeV}$. The energy released if all the atoms in $120g$ of pure $X240$ undergo fission is _____$\times {10}^{25}\mathrm{MeV}$. (Given ${N}_{A}=6\times {10}^{23}$)

A photon is emitted in transition from $n=4\mathrm{to}n=1$ level in hydrogen atom. The corresponding wavelength for this transition is (given, $h=4\times {10}^{-15}\mathrm{eV}s$)