(a) 1.4 10 ^15 m (b) 5.3 10 ^11 m
(c) 2 10 ^13 m (d) 2.8 10 ^35 m
An electron collides with free molecules initially in
its ground state. The collision leaves the molecules
in an excited state that is metastable and does not
decay to the ground state by radiation. Let K be
the sum of the initial kinetic energies of the electron
and the molecule, and P
the sum of their initial
momenta. Let K'and 'P
represent the same
physical quantities after the collision. Then
(a) K K P P ', '
(b) K K P P' , '
(c) K K P P' , '
(d) K K P P' , '
Given below are three schematic graphs of potential
energy V(r) versus distance r for three atomic
particles : electron e,proton (p+) and neutron
(n), in the presence of a nucleus at the origin O.
The radius of the nucleus is r 0. The scale on the V-
axis may not be the same for all figures. The correct
pairing of each graph with the corresponding atomic
particle is
(a) 1, , 2, , 3,n p e
(b) 1, , 2, , 3,p e n
(c) 1, , 2, , 3,e p n
(d) 1, , 2, , 3,p n e
Due to transitions among its first three energy
levels, hydrogenic atom emits radiation at three
discrete wavelengths
1 , , 2 and 3 1 2 3 .Then
(a) 1 2 3 (b) 1 2 3
(c) 1/ 1/ 1 2 1/ 3 (d) 1/ 1 1/ 1/ 2 3
The graph shows the log of activity
(log R) of a radioactive material as a function of
- time t in minutes.
[2011]1]
[2011]1]
[2011]1]
Nuclear physics
1.
[2018]
2.
[2016]
3.
[2015]
The half- life (in minutes) for the decay is closest
to
(a) 2.1 (b) 3.0 (c) 3.9 (d) 4.4
A nuclear fuel rod generates energy at a rate of
5 10^8 watt m/.^3 It is in the shape of a cylinder of
radius 4.0 mm and length 0.20 m.A coolant of specific
heat 4 10^3 J/ (kg-K) flows past it at a rate of
0.2 kg/s. The temperature rise in this coolant is
approximately
(a) 2 C (b) 6 C (c) 12 C (d) 30 C
Carbon -II decays to boron -II according to the
following formula.
12 11
6 C 5 B e ve 0.96
MeV
Assume that positrons ( )e produced in the
decay combine with free electrons in the atmosphere
and annihilate each other almost immediately.Also
assume that the neutrinos ( )ve are massless and
do not interact with the environment .At t =0 we
have 1g of^126 C.If the half -life of the decay
process is t 0 ,the net energy produced between
timet 0 andt 2 t 0 will be nearly
