Current Electricity — Physics STD 12 Science — Question

When the electron in the hydrogen atom jumps from 2^nd orbit to 1^st orbit, the wavelength of radiation emitted is 𝜆. When the electrons jump from 3^rd orbit to 1^st orbit, the wavelength of emitted radiation would be

(a)

(b)

(c)

(d)

Half-life of radioactive substance is :

Assertion :  For best contrast between maxima and minima in the interference pattern of Young’s double slit experiment, the intensity of light emerging out of the two slits should be equal.

Reason     : The intensity of interference pattern is proportional to square of amplitude.

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

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If the assertion and reason both are false.

When wavelength of incident photon is decreased then

(a) Velocity of emitted photo-electron decreases

(b) Velocity of emitted photoelectron increases

(c) Velocity of photoelectron do not charge

(d) Photo electric current increases

A proton exerts a force on a proton which is:

1. Gravitational.
2. Electromagnetic.
3. Nuclear.
4. Weak.

In Bohr model of the hydrogen atom, the lowest orbit corresponds to

(a) Infinite energy	(b) The maximum energy
(c) The minimum energy	(d) Zero energy

A person who is at rest as the charge moves by him will measure.

The photoelectric threshold wavelength of a certain metal is 3000Å. If the radiation of 2000Å is incident on the metal

(a) Electrons will be emitted	(b) Positrons will be emitted
(c) Protons will be emitted	(d) Electrons will not be emitted

The unit of susceptance is.

A free electron is placed in the path of a plane electromagnetic wave. The electron will start moving: