1
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
2
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
3
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
$${{2c} \over v}$$
4
JEE Main 2021 (Online) 25th July Morning Shift
+4
-1
What should be the order of arrangement of de-Broglie wavelength of electron ($$\lambda$$e), an $$\alpha$$-particle ($$\lambda$$a) and proton ($$\lambda$$p) given that all have the same kinetic energy?
A
$$\lambda$$e = $$\lambda$$p = $$\lambda$$$$\alpha$$
B
$$\lambda$$e < $$\lambda$$p < $$\lambda$$$$\alpha$$
C
$$\lambda$$e > $$\lambda$$p > $$\lambda$$$$\alpha$$
D
$$\lambda$$e = $$\lambda$$p > $$\lambda$$$$\alpha$$
JEE Main Subjects
Physics
Mechanics
Electricity
Optics
Modern Physics
Chemistry
Physical Chemistry
Inorganic Chemistry
Organic Chemistry
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