LASER is the acronym for

• Light Amplified by Spontaneous Emission of Radiation

• Light Amplification by Stimulated Absorption of Radiation

• Light Amplification by Stimulated Emission of Radiation

• Light Absorption by Stimulated Emission of Radiation

It is a natural process.

• Stimulated absorption

• Spontaneous emission

• Stimulated emission

• None

The photon emitted by this process can be moved only in the direction of the incident photon.

• Stimulated Emission

• Spontaneous Emission

• Stimulated Absorption

• Coherence

Population inversion means

• Number of atoms in excited state are equal to the number of atoms in the ground state.

• Number of atoms in excited state are more than the number of atoms in the ground state.

• Number of atoms in excited state are less than the number of atoms in the ground state.

• No atom in excited state.

The minimum number of levels required for the condition of population inversion is

• 2

• 4

• 5

• 3

The life time of metastable state is

• smaller than the lifetime of excited state

• equal to the lifetime of excited state

• More than the lifetime of excited state

• Zero

LASER action in He-Ne laser is due to

• Ne

• He

• Ne and He both

• Natural process

The nature of output radiation in He-Ne laser is

• pulse mode

• continuous

• Both

• None

What is the role of Helium in He-Ne laser?

• The condition of population inversion is achieved in He.

• He is responsible of Laser action.

• He atoms excite Ne atoms.

Einstein proved thermodynamically that

• The probability of stimulated absorption is equal to the probability of stimulated emission.

• The probability of stimulated absorption is equal to the probability of spontaneous emission.

• The probability of stimulated emission is equal to the probability of spontaneous emission.