1
JEE Main 2020 (Online) 3rd September Evening Slot
+4
-1
Two sources of light emit X-rays of wavelength 1 nm and visible light of wavelength 500 nm, respectively. Both the sources emit light of the same power 200 W. The ratio of the number density of photons of X-rays to the number density of photons of the visible light of the given wavelengths is :
A
$${1 \over {500}}$$
B
500
C
250
D
$${1 \over {250}}$$
2
JEE Main 2020 (Online) 3rd September Morning Slot
+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
3
JEE Main 2020 (Online) 2nd September Evening Slot
+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
4
JEE Main 2020 (Online) 9th January Evening Slot
+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
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