1
JEE Main 2020 (Online) 3rd September Morning Slot
MCQ (Single Correct Answer)
+4
-1
When the wavelength of radiation falling on a metal is changed from 500 nm to 200 nm, the maximum kinetic energy of the photoelectrons becomes three times larger. The work function of the metal is close to :
A
1.02 eV
B
0.81 eV
C
0.61 eV
D
0.52 eV
2
JEE Main 2020 (Online) 2nd September Evening Slot
MCQ (Single Correct Answer)
+4
-1
A particle is moving 5 times as fast as an electron. The ratio of the de-Broglie wavelength of the particle to that of the electron is 1.878 $$\times$$ 10–4. The mass of the particle is close to
A
1.2 $$\times$$ 10–28 kg
B
9.1 $$\times$$ 10–31 kg
C
4.8 $$\times$$ 10–27 kg
D
9.7 $$\times$$ 10–28 kg
3
JEE Main 2020 (Online) 9th January Evening Slot
MCQ (Single Correct Answer)
+4
-1
The energy required to ionise a hydrogen like ion in its ground state is 9 Rydbergs. What is the wavelength of the radiation emitted when the electron in this ion jumps from the second excited state to the ground state ?
A
35.8 nm
B
11.4 nm
C
8.6 nm
D
24.2 nm
4
JEE Main 2020 (Online) 9th January Evening Slot
MCQ (Single Correct Answer)
+4
-1
An electron of mass m and magnitude of charge |e| initially at rest gets accelerated by a constant electric field E. The rate of change of de-Broglie wavelength of this electron at time t ignoring relativistic effects is :
A
$${{ - h} \over {\left| e \right|Et}}$$
B
$${{ - h} \over {\left| e \right|E\sqrt t }}$$
C
$${{ - h} \over {\left| e \right|E{t^2}}}$$
D
$${{\left| e \right|Et} \over h}$$
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Physics
Mechanics
Electricity
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Modern Physics
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