1
JEE Main 2017 (Online) 8th April Morning Slot
MCQ (Single Correct Answer)
+4
-1
According to Bohr’s theory, the time averaged magnetic field at the centre (i.e. nucleus) of a hydrogen atom due to the motion of electrons in the nth orbit is proportional to : (n = principal quantum number)
A
$${n^{ - 4}}$$
B
$${n^{ - 5}}$$
C
n$$-$$3
D
n$$-$$2
2
JEE Main 2017 (Online) 8th April Morning Slot
MCQ (Single Correct Answer)
+4
-1
Two deuterons undergo nuclear fusion to form a Helium nucleus. Energy released in this process is : (given binding energy per nucleon for deuteron = 1.1 MeV and for helium = 7.0 MeV)
A
30.2 MeV
B
32.4 MeV
C
23.6 MeV
D
25.8 MeV
3
JEE Main 2017 (Offline)
MCQ (Single Correct Answer)
+4
-1
Some energy levels of a molecule are shown in the figure. The ratio of the wavelengths r = $${{\lambda _1}}$$/$${{\lambda _2}}$$, is given by:

A
r = 1/3
B
r = 4/3
C
r = 2/3
D
r = 3/4
4
JEE Main 2017 (Offline)
MCQ (Single Correct Answer)
+4
-1
A radioactive nucleus A with a half life T, decays into a nucleus B. At t = 0, there is no nucleus B. At sometime t, the ratio of the number of B to that of A is 0.3. Then, t is given by :
A
$$t = {T \over {\log (1.3)}}$$
B
$$t = T\log (1.3)$$
C
$$t = {T \over 2}{{\log 2} \over {\log 1.3}}$$
D
$$t = T{{\log 1.3} \over {\log 2}}$$
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Mechanics
Electricity
Optics
Modern Physics
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