51.

Assertion: In a transistor the base is made thin. 

Reason: A thin base makes the transistor stable.

• 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

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: At the first glance, the top surface of the Morpho butterfly's wing appears a beautiful blue-green. If the wing moves the colour changes.

Reason: Different pigments in the wing reflect light at different angles.

• If both assertion and reason are true and reason is 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

Assertion: A famous painting was painted by not using brush strokes in the usual manner, but rather a myriad of small colour dots. In this painting the colour you see at any given place on the painting changes as you move away.

Reason: The angular separation of adjacent dots changes with the distance from the painting.

• 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

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

Assertion:  In He-Ne laser, population inversion takes place between energy levels of neon atoms. 

Reason:  Helium atoms have a meta-stable energy level.

• 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

Assertion: A transistor amplifier in common emitter configuration has a low input impedence.

Reason: The base to emitter region is forward biased.

• 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

Assertion:  Crystalline solids can cause X-rays to diffract. 

Reason:  Interatomic distance in crystalline solids is of the order of 0.1 nm.

• 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

Assertion:  Photoelectric effect demonstrates the wave nature of light.

Reason: The number of photoelectrons is proportional to the frequency of light

• 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