1
JEE Main 2021 (Online) 20th July Morning Shift
+4
-1
A radioactive material decays by simultaneous emissions of two particles with half lives of 1400 years and 700 years respectively. What will be the time after which one third of the material remains ? (Take ln 3 = 1.1)
A
740 years
B
1110 years
C
700 years
D
340 years
2
JEE Main 2021 (Online) 20th July Morning Shift
+4
-1
A nucleus of mass M emits $$\gamma$$ -ray photon of frequency 'v'. The loss of internal energy by the nucleus is :

[Take 'c' as the speed of electromagnetic wave]
A
hv
B
$$hv\left[ {1 + {{hv} \over {2M{c^2}}}} \right]$$
C
$$hv\left[ {1 - {{hv} \over {2M{c^2}}}} \right]$$
D
0
3
JEE Main 2021 (Online) 18th March Evening Shift
+4
-1
The speed of electrons in a scanning electron microscope is 1 $$\times$$ 107 ms-1. If the protons having the same speed are used instead of electrons, then the resolving power of scanning proton microscope will be changed by a factor of :
A
$${1 \over {1837}}$$
B
1837
C
$${\sqrt {1837} }$$
D
$${1 \over {\sqrt {1837} }}$$
4
JEE Main 2021 (Online) 18th March Evening Shift
+4
-1
The decay of a proton to neutron is :
A
always possible as it is associated only with $$\beta$$+ decay
B
possible only inside the nucleus
C
not possible as proton mass is less than the neutron mass
D
not possible but neutron to proton conversation is possible
JEE Main Subjects
Physics
Mechanics
Electricity
Optics
Modern Physics
Chemistry
Physical Chemistry
Inorganic Chemistry
Organic Chemistry
Mathematics
Algebra
Trigonometry
Coordinate Geometry
Calculus
EXAM MAP
Joint Entrance Examination