Modern Physics PYQ — Page 17

A particular hydrogen like ion emits radiation of frequency $2.92\times {10}^{15}\mathrm{Hz}$ when it makes transition from $n=3$ to $n=1$. The frequency in $\mathrm{Hz}$ of radiation emitted in transition from $n=2$ to $n=1$ will be:

Choose the correct waveform that can represent the voltage across $R$ of the following circuit, assuming the diode is ideal one: 

Which level of the single ionized carbon has the same energy as the ground state energy of hydrogen atom?

$X$ different wavelength may be observed in the spectrum from a hydrogen sample if the atoms are excited to states with principal quantum number $n=6$? The value of $X$ is

In a photoelectric experiment, increasing the intensity of incident light:

LED is constructed from $Ga-As-P$ semiconducting material. The energy gap of this LED is $1.9\mathrm{eV}$. Calculate the wavelength of light emitted and its colour. $h=6.63\times {10}^{-34}J-s$ and $c=3\times {10}^{8}m{s}^{-1}$

According to Bohr atom model, in which of the following transitions will the frequency be maximum?

In a photoelectric experiment, ultraviolet light of wavelength $280\mathrm{nm}$ is used with lithium cathode having work function $\phi =2.5\mathrm{eV}$. If the wavelength of incident light is switched to $400\mathrm{nm}$, find out the change in the stopping potential. $(h=6.63\times {10}^{-34}Js,c=3\times {10}^{8}{ms}^{-1})$

For the circuit shown below, calculate the value of ${I}_{z}:$ 

What should be the order of arrangement of de-Broglie wavelength of electron $({\lambda }_{e})$, an $\alpha$-particle $({\lambda }_{\alpha })$ and proton $({\lambda }_{p})$ given that all have the same kinetic energy ?

A circuit is arranged as shown in figure. The output voltage ${V}_{o}$ is equal to __________ $V.$ 

A particle is travelling $4$ times as fast as an electron. Assuming the ratio of de-Broglie wavelength of a particle to that of electron is $2:1,$ the mass of the particle is :-

An oil drop of the radius $2\mathrm{mm}$ with a density $3g$ ${\mathrm{cm}}^{-3}$ is held stationary under a constant electric field $3.55\times {10}^{5}V{m}^{-1}$ in the Millikan's oil drop experiment. What is the number of excess electrons that the oil drop will possess? $(\text{consider}g=9.81m{s}^{-2})$.

In the given figure, each diode has a forward bias resistance of $30\Omega$ and infinite resistance in reverse bias. The current ${I}_{1}$ will be : 

The decay of a proton to neutron is :

A zener diode of power rating $2W$ is to be used as a voltage regulator. If the zener diode has a breakdown of $10V$ and it has to regulate voltage fluctuated between $6V$ and $14V$, the value of ${R}_{s}$ for safe operation should be _____ $\Omega$ . 

The de-Broglie wavelength of a particle having kinetic energy $E$ is $\lambda .$ How much extra energy must be given to this particle so that the de-Broglie wavelength reduces to $75%$ of the initial value?

A certain metallic surface is illuminated by monochromatic radiation of wavelength $\lambda$. The stopping potential for photoelectric current for this radiation is $3{V}_{0}.$ If the same surface is illuminated with a radiation of wavelength $2\lambda ,$ the stopping potential is ${V}_{0}.$ The threshold wavelength of this surface for photoelectric effect is___________$\lambda .$

A $5V$ battery is connected across the points $X$ and $Y$. Assume ${D}_{1}$ and ${D}_{2}$ to be normal silicon diodes. Find the current supplied by the battery if the $+ve$ terminal of the battery is connected to point $X$. 

Consider the following statements: $A$. Atoms of each element emit characteristics spectrum. $B.$ According to Bohr's Postulate, an electron in a hydrogen atom revolves in a certain stationary orbit. $C.$ The density of nuclear matter depends on the size of the nucleus. $D.$ A free neutron is stable but a free proton decay is possible. $E.$ Radioactivity is an indication of the instability of nuclei. Choose the correct answer from the options given below.

The zener diode has a ${V}_{z}=30V$. The current passing through the diode for the following circuit is___$\mathrm{mA}.$ 

In the following logic circuit the sequence of the inputs $A,B$ are $(0,0),(0,1),(1,0)$ and $(1,1).$ The output $Y$ for this sequence will be : 

The truth table for the following logic circuit is : 

Identify the logic operation carried out by the given circuit: