Question

Which of the following is conserved when light waves interfere?
A. Momentum
B. Amplitude
C. Energy
D. Intensity

Answer 1

Hint:The phenomenon of superposition of two or more waves is called interference of the waves. When the light waves interfere, the resultant wave has a new intensity. Interference of light waves is said to be the distribution of energy.

Complete answer:
Let us first understand what is interference of waves. When two or more waves meet, a new wave (resultant wave) is formed. This property of waves is termed as superposition of waves.
The phenomenon of superposition of two or more waves is called interference of the waves.
From the electromagnetic theory we know that light is a wave. Therefore, light from different sources also undergo interference.

Suppose there are two sources of light placed at some distance apart. Now, both the sources will emit light waves of some intensities in all the directions and the waves from the two sources meet if they undergo interference.

When the light interferes, the resultant wave has a new intensity. Therefore, there will be some points where the intensity of light will be minimum and there will be some points where the intensity will be maximum. However, the total energy of the system will remain constant. This is because there is no conversion of energy from one form to another in this process.

Therefore, we can say that the energy at different points is different but the total energy is conserved. Hence, interference of light waves is said to be the distribution of energy.

Note: The amplitude of a wave depends on the intensity of the wave. The intensity is directly proportional to the square of the amplitude of the wave. We discussed that the intensity of light is different at different places. Therefore, the amplitude of the resultant waves is different at different places.