1
JEE Main 2021 (Online) 26th August Morning Shift
+4
-1
A particular hydrogen like ion emits radiation of frequency 2.92 $$\times$$ 1015 Hz when it makes transition from n = 3 to n = 1. The frequency in Hz of radiation emitted in transition from n = 2 to n = 1 will be :
A
0.44 $$\times$$ 1015
B
6.57 $$\times$$ 1015
C
4.38 $$\times$$ 1015
D
2.46 $$\times$$ 1015
2
JEE Main 2021 (Online) 27th July Evening Shift
+4
-1
An electron and proton are separated by a large distance. The electron starts approaching the proton with energy 3 eV. The proton captures the electron and forms a hydrogen atom in second excited state. The resulting photon is incident on a photosensitive metal of threshold wavelength 4000$$\mathop A\limits^o$$. What is the maximum kinetic energy of the emitted photoelectron?
A
7.61 eV
B
1.41 eV
C
3.3 eV
D
No photoelectron would be emitted
3
JEE Main 2021 (Online) 27th July Evening Shift
+4
-1
Consider the following statements :

A. Atoms of each element emit characteristics spectrum.

B. According to Bohr's Postulate, an electron in a hydrogen atom, revolves in a certain stationary orbit.

C. The density of nuclear matter depends on the size of the nucleus.

D. A free neutron is stable but a free proton decay is possible.

E. Radioactivity is an indication of the instability of nuclei.

Choose the correct answer from the options given below :
A
A, B, C, D and E
B
A, B and E only
C
B and D only
D
A, C and E only
4
JEE Main 2021 (Online) 25th July Evening Shift
+4
-1
An electron moving with speed v and a photon moving with speed c, have same D-Broglie wavelength. The ratio of kinetic energy of electron to that of photon is :
A
$${{3c} \over v}$$
B
$${v \over {3c}}$$
C
$${v \over {2c}}$$
D
$${{2c} \over v}$$
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