1
JEE Main 2021 (Online) 31st August Evening Shift
MCQ (Single Correct Answer)
+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
2
JEE Main 2021 (Online) 31st August Evening Shift
MCQ (Single Correct Answer)
+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
$${{{m_p}} \over {{m_e}}}$$
3
JEE Main 2021 (Online) 31st August Morning Shift
MCQ (Single Correct Answer)
+4
-1
A moving proton and electron have the same de-Broglie wavelength. If K and P denote the K.E. and momentum respectively. Then choose the correct option :
A
Kp < Ke and Pp = Pe
B
Kp = Ke and Pp = Pe
C
Kp < Ke an Pp < Pe
D
Kp > Ke and Pp = Pe
4
JEE Main 2021 (Online) 27th August Evening Shift
MCQ (Single Correct Answer)
+4
-1
A monochromatic neon lamp with wavelength of 670.5 nm illuminates a photo-sensitive material which has a stopping voltage of 0.48 V. What will be the stopping voltage if the source light is changed with another source of wavelength of 474.6 nm?
A
0.96 V
B
1.25 V
C
0.24 V
D
1.5 V
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