Question

For fission of uranium $$_{92}^{235}U,$$  one needs

A. very fast neutrons (a few electrons volts)
B. low energy neutrons $$\left( { \approx 0.04\,eV\,{\text{at}}\,300K} \right)$$
C. a moderator making neutrons slow
D. both (B) and (C)  
Answer :   both (B) and (C)
Solution :
Fission of $$_{92}^{235}U$$  is possible by only slow neutrons. To produce slow neutrons, one has to use moderators so that fission is possible.

Releted MCQ Question on
Modern Physics >> Atoms or Nuclear Fission and Fusion

Releted Question 1

The equation
$$4_1^1{H^ + } \to _2^4H{e^{2 + }} + 2{e^ - } + 26MeV$$       represents

A. $$\beta $$ -decay
B. $$\gamma $$ -decay
C. fusion
D. fission
Releted Question 2

Fast neutrons can easily be slowed down by

A. the use of lead shielding
B. passing them through water
C. elastic collisions with heavy nuclei
D. applying a strong electric field
Releted Question 3

In the nuclear fusion reaction
$$_1^2H + _1^3H \to _2^4He + n$$
given that the repulsive potential energy between the two nuclei is $$ \sim 7.7 \times {10^{ - 14}}J,$$    the temperature at which the gases must be heated to initiate the reaction is nearly
[Boltzmann’s Constant $$k = 1.38 \times {10^{ - 23}}J/K$$    ]

A. $${10^7}K$$
B. $${10^5}K$$
C. $${10^3}K$$
D. $${10^9}K$$
Releted Question 4

The binding energy per nucleon of deuteron $$\left( {_1^2H} \right)$$ and helium nucleus $$\left( {_2^4He} \right)$$  is $$1.1\,MeV$$  and $$7\,MeV$$  respectively. If two deuteron nuclei react to form a single helium nucleus, then the energy released is

A. $$23.6\,MeV$$
B. $$26.9\,MeV$$
C. $$13.9\,MeV$$
D. $$19.2\,MeV$$

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