Physics Modern Physics questions from NEET UG 2021.
The photoelectric effect was explained by
For the given circuit, the input digital signals are applied at the terminals $A,B$ and $C$. What would be the output at the terminal $y$ ?  
A radioactive nucleus $\begin{matrix}A \\ Z\end{matrix}X$ undergoes spontaneous decay in the sequence $\begin{matrix}A \\ Z\end{matrix}X\rightarrow \begin{matrix} \\ (Z-1)\end{matrix}B\rightarrow \begin{matrix} \\ (Z-3)\end{matrix}C\rightarrow \begin{matrix} \\ (Z-2)\end{matrix}D$, where $Z$ is the atomic number of element $X$. The possible decay particles in the sequence are:
Consider the following statements (A) and (B) and identify the correct answer. (A) A Zener diode is connected in reverse bias when used as a voltage regulator. (B) The potential barrier of $p-n$ junction lies between $0.1V$ to $0.3V$.
The number of photons per second on an average emitted by the source of monochromatic light of wavelength $600\mathrm{nm}$, when it delivers the power of $3.3\times {10}^{-3}W$ will be $:(h=6.6\times {10}^{-34}Js)$
The electron concentration in an undefined $n$-type semiconductor is the same as hole concentration in a undefined $p$-type semiconductor. An external field (electric) is applied across each of them. Compare the currents in them.
A nucleus with mass number $240$ breaks into two fragments each of mass number $120,$ the binding energy per nucleon of unfragmented nuclei is $7.6\mathrm{MeV}$ while that of fragments is $8.5\mathrm{MeV}$. The total gain in the binding energy in the process is :
An electromagnetic wave of wavelength $\lambda$ is incident on a photosensitive surface of negligible work function. If $m$ mass is of photoelectron emitted from the surface has de-Broglie wavelength ${\lambda }_{d}$, then :
The half-life of a radioactive nuclide is $100$ hours. The fraction of original activity that will remain after $150$ hours would be :