Question Answers

Wave Optics

1. Can the two independent source of light produce interference?

No, the two source of light cannot produce interference. It is because the light waves emitted by two different sources may not have constant phase difference though they may have equal frequency and wavelength i. e, they are not coherent sources. Hence, sustained interference pattern will not be obtained.

2. What do you understand by coherent sources?

The two sources of light, which emit light waves of the same wavelength which are always in phase with each other or have a constant phase difference are called coherent sources. In practice, two independent source of light cannot be coherent. This is because of random emission of light waves from their atoms and so the resultant waves are out of phase.

3. Is the law of conservation of energy obeyed in case of interference of light? Explain.

Yes, the law of conservation of energy is obeyed in case of interference of light. During, interference, the two waves from coherent sources superimpose to produce a non-uniform distribution of energy. The energy is higher at the bright fringe and lower at the dark fringe. The energy from the dark portion is transferred to the bright fringe and hence, the total energy remains constant.

4. What are coherent sources of light? Can two different bulbs, similar in all respects, act as coherent sources?

The two sources of light, which emit light waves of the same wavelength which are always in phase with each other or have a constant phase difference are called coherent sources.

In practice, two independent source of light cannot be coherent. This is because of random emission of light waves from their atoms and so the resultant waves are out of phase. The light waves emitted by two different sources may not have constant phase difference though they may have equal frequency and wavelength i.e., they are not coherent sources. Thus, the two different bulbs, similar in all respects, cannot act as coherent sources.

5. What are the conditions of sustained interference of light?

The conditions of sustained interference of light is,

1. The two sources must be coherent.

2. The source should be monochromatic

3. The two sources must be close to each other

4. The two sources should be narrow