JEE Main Physics — Modern Physics previous year questions with solutions.
For the given circuit, the power across zener diode is _____ $\mathrm{mW}$. 
In a semiconductor, the number density of intrinsic charge carriers at $27^{\circ}C$ is $1.5\times {10}^{16}{m}^{-3}$. If the semiconductor is doped with an impurity atom, the hole density increases to $4.5\times {10}^{22}{m}^{-3}$. The electron density in the doped semiconductor is _______$\times {10}^{9}{m}^{-3}$
The output of the given combination gates represents: 
Draw the output signal $Y$ in the given combination of gates. 
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 $X$. 
An electron of mass ${m}_{e}$ and a proton of mass ${m}_{p}=1836{m}_{e}$ are moving with the same speed. The ratio of their de Broglie wavelength $\frac{{\lambda }_{electron}}{{\lambda }_{proton}}$ will be :
Given below are two statements: Statement I : $p-n$ junction diodes can be used to function as a transistor, simply by connecting two diodes, back to back, which acts as the base terminal Statement II: In the study of transistors, the amplification factor $\beta$ indicates ratio of the collector current to the base current. In the light of the above statements, choose the correct answer from the options given below.
Find the truth table for the function $Y$ of $A$ and $B$ represented in the following figure. 
In a photoelectric experiment, increasing the intensity of incident light:
In a given circuit diagram, a $5V$ zener diode along with a series resistance is connected across a $50V$ power supply. The minimum value of the resistance required, if the maximum zener current is $90\mathrm{mA}$ will be $\text{Ω.}$ 
From the given data, the amount of energy required to break the nucleus of aluminium $\mathrm{Al}1327$ is __________$x\times {10}^{-3}J$ Mass of neutron $=1.00866u$ Mass of proton $=1.00726u$ Mass of Aluminium nucleus $=27.18846u$ (Assume $1u$ corresponds to $xJ$ of energy) (Round off to the nearest integer)
Two identical photocathodes receive the light of frequencies ${f}_{1}$ and ${f}_{2}$ respectively. If the velocities of the photo-electrons coming out are ${v}_{1}$ and ${v}_{2}$ respectively, then
A monochromatic neon lamp with wavelength of $670.5\mathrm{nm}$ illuminates a photo-sensitive material which has a stopping voltage of $0.48V$. What will be the stopping voltage if the source light is changed with another source of wavelength of $474.6\mathrm{nm}$ ?
An electron of mass ${m}_{e}$ and a proton of mass ${m}_{P}$ are accelerated through the same potential difference. The ratio of the de-Broglie wavelength associated with the electron to that with the proton is
A particle of mass $4M$ at rest disintegrates into two particles of mass $M$ and $3M$, respectively, having non zero velocities. The ratio of de-Broglie wavelength of particle of mass $M$ to that of mass $3M$ will be:
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 : 
A nucleus with mass number $184$ initially at rest emits an $\alpha -$particle. If the $Q$ value of the reaction is $5.5\mathrm{MeV},$ calculate the kinetic energy of the $\alpha -$ particle.
A particle of mass $m$ moves in a circular orbit in a central potential field $U(r)={U}_{0}{r}^{4}.$ If Bohr's quantization conditions are applied, radii of possible orbitals ${r}_{n}$ vary with ${n}^{\frac{1}{\alpha }}$, where $\alpha$ is _______ .
In the logic circuit shown in the figure, if input $A$ and $B$ are $0$ to $1$ respectively, the output at $Y$ would be $x$. The value of $x$ is _________. 
According to Bohr atom model, in which of the following transitions will the frequency be maximum?
An electron moving with speed $v$ and a photon moving with speed $c$, have the same D-Broglie wavelength. The ratio of the kinetic energy of the electron to that of a photon is:
Imagine that the electron in a hydrogen atom is replaced by a muon $(\mu ).$ The mass of muon particle is $207$ times that of an electron and charge is equal to the charge of an electron. The ionization potential of this hydrogen atom will be:-
Identify the logic operation carried out. 
Consider a situation in which reverse biased current of a particular $P-N$ junction increases when it is exposed to a light of wavelength $\leq 621\mathrm{nm}.$ During this process, enhancement in carrier concentration takes place due to generation of hole-electron pairs. The value of band gap is nearly.