1
JEE Main 2021 (Online) 1st September Evening Shift
+4
-1
The temperature of an ideal gas in 3-dimensions is 300 K. The corresponding de-Broglie wavelength of the electron approximately at 300 K, is :

[me = mass of electron = 9 $$\times$$ 10$$-$$31 kg, h = Planck constant = 6.6 $$\times$$ 6.6 $$\times$$ 10$$-$$34 Js, kB = Boltzmann constant = 1.38 $$\times$$ 10$$-$$23 JK$$-$$1]
A
6.26 nm
B
8.46 nm
C
2.26 nm
D
3.25 nm
2
JEE Main 2021 (Online) 1st September Evening Shift
+4
-1
The half life period of radioactive element x is same as the mean life time of another radioactive element y. Initially they have the same number of atoms. Then :
A
x-will decay faster than y.
B
y-will decay faster than x.
C
x and y have same decay rate initially and later on different decay rate.
D
x and y decay at the same rate always.
3
JEE Main 2021 (Online) 31st August Evening Shift
+4
-1
A free electron of 2.6 eV energy collides with a H+ ion. This results in the formation of a hydrogen atom in the first excited state and a photon is released. Find the frequency of the emitted photon. (h = 6.6 $$\times$$ 10$$-$$34 Js)
A
1.45 $$\times$$ 1016 MHz
B
0.19 $$\times$$ 1015 MHz
C
1.45 $$\times$$ 109 MHz
D
9.0 $$\times$$ 1027 MHz
4
JEE Main 2021 (Online) 31st August Evening Shift
+4
-1
Consider two separate ideal gases of electrons and protons having same number of particles. The temperature of both the gases are same. The ratio of the uncertainty in determining the position of an electron to that of a proton is proportional to :-
A
$${\left( {{{{m_p}} \over {{m_e}}}} \right)^{3/2}}$$
B
$$\sqrt {{{{m_e}} \over {{m_p}}}}$$
C
$$\sqrt {{{{m_p}} \over {{m_e}}}}$$
D
$${{{m_p}} \over {{m_e}}}$$
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