51.

At 0 K temperature, a p-type semiconductor

• does not have any charge carriers

• has few holes but no free electrons

• has few holes and few free electrons 

• has equal number of holes and free electrons

The speed of an electron having a wavelength of 10^-10 m is

• 7.25 × 10⁶ m/s

• 5.25 × 10⁶ m/s

• 6.26 × 10⁶ m/s

• 4.24 × 10⁶ m/s

The potential barrier, in the depletion layer, is due to 

• ions

• electrons

• holes

• forbidden band

Brilliance of diamond is due to

• shape

• reflection

• cutting

• total internal reflection

The Cauchy's dispersion formula is

• n = A + Bλ^-2 + Cλ^-4

• n = A + Bλ^-2 + Cλ⁴

• n = A + Bλ² + Cλ^-4

• n = A + Bλ² + Cλ⁴

Golden view of sea shell is due to

• diffraction

• polarisation

• dispersion

• reflection

Assertion: Coloured spectrum is seen when we look through a muslin cloth. 

Reason:  It is due to the diffraction of white light on passing through fine slits

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

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

• If the assertion is true but the reason is false.

• If both assertion and reason are false.

Assertion:  When tiny circular obstacle is placed in the path of light from some distance, a bright spot is seen at the centre of the shadow of the obstacle. 

Reason: Destructive interference occurs at the centre of the shadow.

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

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

• If the assertion is true but the reason is false

• If both assertion and reason are false.

Assertion:  Quasar emits radiowaves more than radio galaxy. 

Reason:  Quasar has very small size

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

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

• If the assertion is true but the reason is false.

• If both assertion and reason are false.

Assertion:  S.I. units are logical and coherent. 

Reason: S.l. system of units is a rationalised system.

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

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

• If the assertion is true but the reason is false.

• If both assertion and reason are false.