Modern Physics PYQ

A particle of mass $m$ is moving around the origin with a constant force $F$ pulling it towards the origin. If Bohr model is used to describe its motion, the radius $r$ of the $n^{\text {th }}$ orbit and the particle's speed $v$ in the orbit depend on $n$ as

A full wave rectifier circuit with diodes $\left(D_1\right)$ and $\left(D_2\right)$ is shown in the figure. If input supply voltage $V_{\text {in }}=220 \sin (100 \pi t)$ volt, then at $t=15 \mathrm{msec}$ 

The output $(\mathrm{Y})$ of the given logic implementation is similar to the output of an/a _____ gate. 

De-Broglie wavelength of an electron orbiting in the $n=2$ state of hydrogen atom is close to (Given Bohr radius $=0.052 \mathrm{~nm}$ )

Which of the following options represent the variation of photoelectric current with property of light shown on the x -axis? 

A logic circuit provides the output $Y$ as per the following truth table : \begin{array}{|l|l|l|}\hlineA & B & Y \\\hline 0 & 0 & 1 \\0 & 1 & 0 \\1 & 0 & 1 \\1 & 1 & 0 \\\hline\end{array} The expression for the output $Y$ is :

Water is used as a coolant in a nuclear reactor because of its

The spectral series which corresponds to the electronic transition from the levels $n_2=5,6, \ldots$ to the level $n_1=4$ is

Match List I with List II. \begin{array}{|l|l|l|l|}\hline & {|c|}{\begin{array}{c} List I \\(Spectral Lines of \\Hydrogen for \\transitions from)\end{array}} & & {|c|}{\begin{array}{l} List II \\(Wavelengths (nm))\end{array}} \\\hline A. & n_2=3 to m_1=2 & I. & 410.2 \\\hline B. & n_2=4 to m_1=2 & II. & 434.1 \\\hline C. & n_2=5 to n_1=2 & III. & 656.3 \\\hline D. & n_2=6 to n_1=2 & IV. & 486.1 \\\hline\end{array} Choose the correct answer from the options given below:

Select the correct statements among the following : A. Slow neutrons can cause fission in ${ }_{92}^{235} \mathrm{U}$ than fast neutrons. B. $\alpha$-rays are Helium nuclei. C. $\beta$-rays are fast moving electrons or positrons.| D. $\gamma$-rays are electromagnetic radiations of wavelengths larger than X-rays. Choose the most appropriate answer from the options given below

 In the nuclear emission stated above, the mass number and atomic number of the product $Q$ respectively, are

Some energy levels of a molecule are shown in the figure with their wavelengths of transitions. Then: 

An electron and an alpha particle are accelerated by the same potential difference. Let $\lambda_{\varepsilon}$ and $\lambda_a$ denote the de-Broglie wavelengths of the electron and the alpha particle, respectively, then:

The output $Y$ for the inputs $A$ and $B$ of the given logic circuit is : 

The graph which shows the variation of $\left(\frac{1}{\lambda^2}\right)$ and its kinetic energy, $E$ is (where $\lambda$ is de Broglie wavelength of a free particle):

When the output of an OR gate is applied as input to a NOT gate, then the combination acts as a

If $\phi$ is the work function of photosensitive material in eV and light of wavelength of numerical value $\lambda=\frac{h c}{e}$ metre, is incident on it with energy above its threshold value at an instant then the maximum kinetic energy of the photo-electron ejected by it at that instant (Take $h$-Plank's constant, $c$-velocity of light in free space) is (in SI units):

Consider the following statements A and B and identify the correct answer:  A. For a solar-cell, the I-V characteristics lies in the IV quadrant of the given graph. B. In a reverse biased pn junction diode, the current measured in $(\mu \mathrm{A})$, is due to majority charge carriers.

 The I-V characteristics shown above are exhibited by a

Given below are two statements: Statement I: Atoms are electrically neutral as they contain equal number of positive and negative charges. Statement II: Atoms of each element are stable and emit their characteristic spectrum. In the light of the above statements, choose the most appropriate answer from the options given below.

The output ( $Y$ ) of the given logic gate is similar to the output of an/a 

If $c$ is the velocity of light in free space, the correct statements about photon among the following are: A. The energy of a photon is $E=h v$. B. The velocity of a photon is $c$. C. The momentum of a photon, $p=\frac{h \nu}{c}$. D. In a photon-electron collision, both total energy and total momentum are conserved. E. Photon possesses positive charge. Choose the correct answer from the options given below: