1
IAT (IISER) 2020
MCQ (Single Correct Answer)
+4
-1

An electron of mass $m_e$ has a speed $u_n$ in the $n^{\text {th }}$ Bohr orbit of a hydrogen atom. The normalized speed $V_n$ is given as $V_n=u_n / c=1 / 685$ and the mass of the electron in the units of energy is given as $M_e=m_e c^2=0.51 \times 10^6 \mathrm{eV}$, where $c$ is the velocity of light in a vacuum. It is given that $\frac{e^2}{2 \epsilon_0 h c}=1 / 137$. The Planck's constant h is given as $4.13 \times 10^{-15} \mathrm{eV}-\mathrm{sec}$. The electron makes a transition from $n^{\text {th }}$ orbit to the ground state of the atom. What is the frequency of the emitted photon?

A
$3.29 \times 10^{15} \mathrm{~Hz}$
B
$2.47 \times 10^{15} \mathrm{~Hz}$
C
$2.93 \times 10^{15} \mathrm{~Hz}$
D
$3.16 \times 10^{15} \mathrm{~Hz}$
2
IAT (IISER) 2020
MCQ (Single Correct Answer)
+4
-1
In the photoelectric effect experiment, the frequency of the incident light is changed from red to blue while keeping the energy per unit area per unit time of the incident radiation fixed. What will happen to the saturation current?
A
Saturation current doesn't depend on frequency and therefore will be same for red and blue light
B
Saturation current depends on intensity and therefore will be same for red and blue light
C
Saturation current for blue colour light is larger than red colour light
D
Saturation current for blue colour light is smaller than red colour light
3
IAT (IISER) 2020
MCQ (Single Correct Answer)
+4
-1
An ideal rigid diatomic gas undergoes expansion at constant pressure when $\Delta Q$ heat is added to it. What is the ratio of the change in the internal energy $\Delta U$ to the heat supplied $\Delta Q$ ?
A
$\frac{\Delta U}{\Delta Q}=\frac{3}{5}$
B
$\frac{\Delta U}{\Delta Q}=\frac{5}{7}$
C
$\frac{\Delta U}{\Delta Q}=\frac{7}{9}$
D
$\frac{\Delta U}{\Delta Q}=\frac{2}{3}$
4
IAT (IISER) 2020
MCQ (Single Correct Answer)
+4
-1
The fundamental constants are given to be permittivity constant $\left(\epsilon_0\right)$, Planck's constant $(h)$, velocity of light $(c)$, Newton's constant $(G)$ and Boltzmann's constant $\left(k_B\right)$. Which of the following quantities constructed out of the above constant has the dimensions of an electric charge?
A
$\sqrt{\frac{h G}{\epsilon_0^3}}$
B
$\sqrt{h c}$
C
$k_B \sqrt{h c}$
D
$\sqrt{\epsilon_0 h c}$
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