31.

CO₂ laser uses

• microwaves

• infra red

• ultra violet

• visible light

In an AC circuit the potential differences across an inductance and resistance joined in series are respectively 16 V and 20 V. The total potential difference of the source is

• 20.0 V

• 25.6 V

• 31.9 V

• 53.5 V

The focal length of the objective and eye lenses of a microscope are 1.6 cm and 2.5 cm respectively. The distance between the two lenses is 21. 7 cm. If the final image is formed at infinity. What is the linear magnification?

• 11

• 110

• 1.1

• 44

The magnetic susceptibility of an ideal diamagnetic substance is

• $-$1

• 0

• +1

• ∞

Assertion: : A current continues to follow in superconducting coil even after switch is off.

Reason: Superconducting coils show Meissner effect.

• 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: Dipole oscillations produce electromagnetic waves.

Reason: Accelerated charge produces electromagnetic waves.

• 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

Asserion: : NAND is a universal gate.

Reason: It can be used to describe all other logic gates.

• 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 a cavity within a conductor, the electric field is zero.

Reason: Charges in a conductor reside only at its surface.

• 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:  Ferro magnetic substances become paramagnetic above Curie temperature. 

Reason:  Domains are destroyed at high temperature.

• 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: Ohm's law is applicable for all conducting elements.

Reason: Ohm's law is a fundamental law.

• 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