51.

Assertion: Radioactive nuclei emit  β^- particles.

Reason: Electrons exist inside the nucleus.

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

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

• if assertion is true but reason is false

• If both assertion and reason are false statements

Assertion: The resistivity of a semiconductor increases with temperature. 

Reason:  The atoms of a semiconductor vibrate with larger amplitude at higher temperatures thereby increasing its resistivity.

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

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

• if assertion is true but reason is false

• if both assertion and reason are false statements

Assertion: Bohr had to postulate that the electrons in stationary orbits around the nucleus do not radiate. 

Reason:  According to classical physics all moving electrons radiate.

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

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

• if assertion is true but reason is false

• if both assertion and reason are false statements

Assertion: The possibility of an electric bulb fusing is higher at the time of switching on and off.

Reason: Inductive effects produce a surge at the time of switch-off and switch-on.

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

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

• if assertion is true but reason is false

• if both assertion and reason are false statements

Assertion:  The stars twinkle while the planets do not. 

Reason: The stars are much bigger in size than the planets.

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

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

• if assertion is true but reason is false

• if both assertion and reason are false statements

Assertion:  A beam of charged particles is employed in the treatment of cancer. 

Reason: Charged particles on passing through a material medium lose their energy by causing ionization of the atoms along their path.

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

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

• if assertion is true but reason is false

• if both assertion and reason are false statements

Assertion: Owls can move freely during night. 

Reason: They have large number of rods on their retina.

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

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

• if assertion is true but reason is false

• if both assertion and reason are false statements

Assertion:   Microwave communication is peferred over optical communication. 

Reason: Microwaves provide large number of channels and bandwidth compared to optical signals.

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

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

• if assertion is true and reason is false

• if both assertion and reason are false statements

Assertion: Neutrons penetrate matter more readily as compared to protons.

Reason: Neutrons are slightly more massive than protons.

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

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

• if assertion is true but reason is false

• if both assertion and reason are false statements

Assertion: In high latitudes one sees colourful curtains of light hanging down from high altitudes. 

Reason: The high energy charged particles from the are deflected to polar regions by the magnetic field of the earth.

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

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

• if assertion is true but reason is false

• if both assertion and reason are false statements