NEET UG Physics — Modern Physics previous year questions with solutions.
The following figure shows a logic gate circuit with two inputs $A$ and $B$ and the output $Y$. The voltage waveforms of $A, B$ and $Y$ are as given   The logic gate is
The decay constant of a radio isotope is $\lambda$. If $A_1$ and $\mathrm{A}_2$ are its activities at times $\mathrm{t}_1$ and $\mathrm{t}_2$ respectively, the number of nuclei which have decayed during the time $\left(\mathrm{t}_1-\mathrm{t}_2\right)$
The activity of a radioactive sample is measured as $\mathrm{N}_0$ counts per minute at $\mathrm{t}=0$ and $\mathrm{N}_0 / \mathrm{e}$ counts per minute at $\mathrm{t}=5 \mathrm{~min}$. The time (in minute) at which the activity reduces to half its value is
A beam of cathode rays is subjected to crossed Electric ( $E$ ) and Magnetic fields $(B)$. The fields are adjusted such that the beam is not deflected. The specific charge of the cathode rays is given by (where $V$ is the potential difference between cathod and anode)
To get an output $Y=1$ from the circuit shown below, the input must be  
A transistor is operated in common-emitter configuration at $\mathrm{V}_{\mathrm{C}}=2 \mathrm{~V}$ such that a change in the base current from $100 \mu \mathrm{A}$ to $200 \mu \mathrm{A}$ produces a change in the collector current from $5 \mathrm{~mA}$ to $10 \mathrm{~mA}$. The current gain is :
The symbolic representation of four logic gates The logic symbols for OR, NOT and NAND gates are respectively 
The number of photoelectrons emitted for light of a frequency $v$ (higher than the threshold frequency $v_0$ ) is proportional to
The number of beta particles emitted by a radioactive substance is twice the number of alpha particles emitted by it. The resulting daughter is an
The ionization energy of the electron in the hydrogen atom in its ground state is $13.6 \mathrm{eV}$. The atoms are excited to higher energy levels to emit radiations of 6 wavelengths. Maximum wavelength of emitted radiation corresponds to the transition between
In the nuclear decay given below $$ { }_{\mathrm{Z}}^{\mathrm{A}} \mathrm{X} \longrightarrow{ }_{\mathrm{Z}+1}^{\mathrm{A}} \mathrm{Y} \longrightarrow{ }_{\mathrm{Z}-1}^{\mathrm{A}-4} \mathrm{~B}^* \longrightarrow{ }_{\mathrm{Z}-1}^{\mathrm{A}-4} \mathrm{~B} \text {, } $$ the particles emitted in the sequence are
In the nuclear decay given below : $$ { }_{\mathrm{A}}^{\mathrm{A}} \mathrm{X} \longrightarrow \stackrel{\mathrm{A}}{\mathrm{A}+1} \mathrm{Y} \longrightarrow \mathrm{A}_{\mathrm{A}-4} \mathrm{~B}^* \longrightarrow \stackrel{\mathrm{A}-4}{\mathrm{Z}-1} \mathrm{~B} $$ The particles emitted in the sequence are :
The number of photoelectrons emitted for light of a frequency $\mathrm{v}$ (higher than the threshold frequency $\mathrm{v}_0$ ) is proportional to :
Monochromatic light of wavelength $667 \mathrm{~nm}$ is produced by a helium neon laser. The power emitted is $9 \mathrm{~mW}$. The number of photons arriving per second on the average at a target irradiated by this beam is :
A $p-n$ photodiode is fabricated from a semiconductor with a band gap of $2.5 \mathrm{eV}$. It can detect a signal of wavelength
The figure shows a plot of photo current versus anode potential for a photo sensitive surface for three different radiations. Which one of the following is a correct statement ? 
In a Rutherford scattering experiment when a projectile of charge $Z_1$ and mass $M_1$ approaches a target nucleus of charge $Z_2$ and mass $M_2$, the distance of closest approach is $r_0$. The energy of the projectile is :
A p-n photodiode is fabricated from a semiconductor with a band gap of $2.5 \mathrm{eV}$. It can detect a signal of wavelength :
Monochromatic light of wavelength $667 \mathrm{~nm}$ is produced by a helium neon laser. The power emitted is $9 \mathrm{~mW}$. The number of photons arriving per second on the average at a target irradiated by this beam is
The ionization energy of the electron in the hydrogen atom in its grounds state is $13.6 \mathrm{eV}$. The atoms are excited to higher energy levels to emit radiations of 6 wavelengths. Maximum wavelength of emitted radiation corresponds to the transition between :
In a Rutherford scattering experiment when a projectile of charge $Z_1$ and mass $M_1$ approaches a target nucleus of charge $Z_2$ and mass $\mathrm{M}_2$, the distance of closest approach is $\mathrm{r}_0$. The energy of the projectile is
The number of beta particles emitted by a radioactive substance is twice the number of alpha particles emitted by it. The resulting daughter is an :
Which of the following hormones contains iodine?
The figure shows a plot of photo current versus anode potential for a photo sensitive surface for three different radiations. Which one of the following is a correct statement? 