Two parallel beams of positrons moving in the same direction will

• repel each other

• will not interact with each other

• attract each other

• be deflected normal to the plane containing the two beams

Carbon dating is best suited for determining the age of fossils if their age in years is of the order of

• 10⁸

• 10⁴

• 10⁴

• 10⁶

The dependence of binding energy per nucleon, B_A  on the mass number A, is represented by

134.

Assertion:  ⁹⁰Sr from the radioactive fall out from a nuclear bomb ends up in the bones of human beings through the milk consumed by them. It causes impairment of the production of red blood cells.

Reason: The energies β-particles emitted in the decay of ⁹⁰Sr damage the bone marrow.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are but reason is not the correct explanation of assertion  

• If asserion and reason is false

• If both assertion and reason are false

Assertion: Energy is released in nuclear fission.

Reason: Total binding energy of the fission fragments is larger than the total binding energy of the parent nucleus.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason is false

Assertion:  Heavy water preferred ever ordinary water as a moderator in reactors. 

Reason:  Heavy water, used for slowing down the neutrons, has lesser absorption probability
of neutrons than ordinary water.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false

A proton is about 1840 times heavier than an electron. When it is accelerated by a potential difference of 1 kV, its kinetic energy will be

• 1840 keV

• 1/1840 keV

• 1 keV

• 920 keV

A radioactive substance decays to 1/16^th of its initial activity in 40 days. The half-life of the radioactive substance expressed in days is

• 2.5

• 5

• 10

• 20

A neutron makes a head-on elastic collision with a stationary deuteron. The fractional energy loss of the neutron in the collision is

• 16/81

• 8/9

• 8/27

• 2/3

Nuclear fusion is possible

• only between light nuclei

• only between heavy nuclei

• between both light and heavy nuclei

• only between nuclei which are stable against β-decay