Modern Physics PYQ — Page 19

Two Zener diodes ($A$ and $B$) having breakdown voltages of $6V$ and $4V$ respectively, are connected as shown in the circuit below. The output voltage ${V}_{0}$ variation with input voltage linearly increasing with time, is given by (${V}_{input}=0Vatt=0$)

When a diode is forward biased, it has a voltage drop of $0.5V$ . the safe limit of current through the diode is $10\mathrm{mA}$. If a battery of emf $1.5V$ is used in the circuit, the value of minimum resistance to be connected in series with the diode so that the current does not exceed the safe limit is :

Particle $A$ of mass ${\text{m}}_{\text{A}}=\frac{\text{m}}{2}$ moving along the $\text{x}$ -axis with velocity ${\text{v}}_{0}$ collides elastically with another particle $\text{B}$ at rest having mass ${\text{m}}_{\text{B}}=\frac{\text{m}}{3}$. If both the particles move along the $\text{x}$ -axis after the collision, the change $\Delta \lambda$ in the wavelength of the particle $\text{A}$, in terms of its de-Broglie wavelength $({\lambda }_{0})$ before the collision is:

A particle moving with kinetic energy $E$ has de Broglie wavelength $\lambda$ . If energy $\Delta E$ is added to its energy, the wavelength become $\frac{\lambda }{2}$ . Value of $\Delta E,$ is:

When the wavelength of radiation falling on a metal is changed from $500\mathrm{nm}\mathrm{to}200\mathrm{nm}$, the maximum kinetic energy of the photoelectrons becomes three times larger. The work function of the metal is close to:

The first member of the Balmer series of hydrogen atom has a wavelength of $6561\overset{\circ }{A}$. The wavelength of the second member of the Balmer series (in nm) is_____________

When photon of energy $4.0eV$ strikes the surface of a metal $A,$ the ejected photoelectrons have maximum kinetic energy ${T}_{A}eV$ and de-Broglie wavelength ${\lambda }_{A}.$ The maximum kinetic energy of photoelectrons liberated from another metal $B$ by photon of energy $4.50eV$ is ${T}_{B}=({T}_{A}-1.5)eV.$ If the de-Broglie wavelength of these photoelectrons ${\lambda }_{B}=2{\lambda }_{A},$ then the work function of metal $B$ is:

Which of the following gives a reversible operation?

With increasing biasing voltage of a photo diode, the photocurrent magnitude:

In a hydrogen atom the electron makes a transition from ${(n+1)}^{\mathrm{th}}$ level to the ${n}^{\mathrm{th}}$ level. If $n>>1$, the frequency of radiation emitted is proportional to :

In the line spectra of hydrogen atom, difference between the largest and the shortest wavelengths of the Lyman series is $305\overset{\circ }{A}$. The corresponding difference for the Paschan series in $\overset{\circ }{A}$ is:________

A beam of electromagnetic radiation of intensity $6.4\times { 10}^{ -5} \text{W}/ { \text{cm}}^{2}$ is comprised of wavelength, $\lambda =310nm$ . It falls normally on a metal (work function $\phi =2eV$ ) of surface area of $1{cm}^{2}$ . If one in ${10}^{3}$ photons ejects an election, total number of electrons ejected in $1s$ is ${10}^{x}$ . $(hc=1240eVnm,1eV=1.6\times {10}^{-19}J),$ then $x$ is ___________

Identify the operation performed by the circuit given below : 

An electron of mass $m$ and magnitude of charge $e$ at rest, gets accelerated by a constant electric field $E$. The rate of change of de-Broglie wavelength of this electron at a time $t$ is (ignore relativistic effects)

Given figure shows few data points in a photo-electric effect experiment for a certain metal. The minimum energy for ejection of electrons from its surface is: (Planck's constant $h=6.62\times {10}^{–34}\text{ J.s}$) 

The current $i$ in the network is 

You are given that $\mathrm{Li}37=7.0160u,$Mass of Mass of $\mathrm{He}24=4.0026u$ and Mass of $\mathrm{He}11=1.0079H$ When $20g$ of $\mathrm{Li}37$ is converted into ${}_{2}^{4}$ He by proton capture, the energy liberated, (in $\mathrm{kWh}$ ), is : [Mass of nucleon $=1\mathrm{GeV}/{c}^{2}$]

In the given circuit, value of $Y$ is: 

A particle is moving $5$ times as fast as an electron. The ratio of the de-Broglie wavelength of the particle to that of the electron is $1.878\times {10}^{–4}$. The mass of the particle is close to :

Take the breakdown voltage of the zener diode used in the given circuit as $6\text{V}$. For the input voltage shown in the figure below, the time variation of the output voltage is: (Graphs drawn are schematic and not to the scale) 

The energy required to ionise a hydrogen like ion in its ground state is $9$ Rydbergs. What is the wavelength of the radiation emitted when the electron in this ion jumps from the second excited stale to the ground state?

In the following, digital circuit, what will be the output a '$Z$', when the input $(A,B)$ are $(1,0),(0,0),(1,1),(0,1)$ 

The surface of a metal is illuminated alternately with photons of energies ${E}_{1}=4\mathrm{eV}$ and ${E}_{2}=2.5\mathrm{eV}$ respectively. The ratio of maximum speeds of the photoelectrons emitted in the two cases is $2.$ The work function of the metal in $(\mathrm{eV})$ is..........

An electron (of mass $m$ ) and a photon have the same energy $E$ in the range of a few $eV$. The ratio of the de-Broglie wavelength associated with the electron and the wavelength of the photon is ( $c=$ speed of light in vacuum)