51.

In a Young's double slit experiment the intensity of light when slit is at distance A from central is I. What will be the intensity at the distance of slit is $\frac{\mathrm{\lambda }}{6}$?

• $\frac{\mathrm{I}}{6}$

• $\frac{\mathrm{I}}{12}$

• $\frac{3}{4}\mathrm{I}$

• $\frac{\mathrm{I}}{6}$

A triply ionized beryllium ( Be³⁺ ) has the same orbital radius as the ground state of hydrogen. Then the quantum state n of Be³⁺ is

• n = 1

• n = 2

• n = 3

• n = 4

Assertion:  Sky wave signals are used for long distance radio communication. These signals are in general, less stable than ground wave signals. 

Reason:  The state of ionosphere varies from hour to hour, day to day and season to season.

• 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:  The ratio for time taken for light emission from an atom to that for release of nuclear energy in fission is 1 : 100. 

Reason:  Time taken for the light emission from an atom is of the order of 10^-8 s.

• 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:  Static crashes are heard on radio, when lightning flash occurs in the sky. 

Reason:  Electromagnetic waves having frequency of radio wave range interfere with radio 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.

Assertion:  An electron microscope is based on de Broglie hypothesis. 

Reason:  A beam of electrons behaves as a wave which can be converged by electric and magnetic lenses.

• 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: The resistance of a junction of a spoiled transistor is low when forward biased or reverse biased. 

Reason: The resistance of a junction of a transistor in working order is high always.

• 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.n

Assertion:  Short wave communication over long distance is not possible via ground waves. 

Reason:  The ground waves can bend round the corners ofthe objects on earth.

• 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:  γ-radiation emission occurs after $\mathrm{\alpha } \mathrm{and} \mathrm{\beta }$ decay. 

Reason: Energy levels occur in 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 are false.

Assertion:  The edges of the images of white object formed by a concave mirror on the screen appear white. 

Reason: Concave mirror does not suffer from chromatic aberration.

• 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.