Constructive Interference

Light is a form of electromagnetic wave and is a part of the electromagnetic spectrum. Light is a form of energy that is also referred to as visible light. Visible light has a wavelength range of 400–700 nm. Sun is the main source of light on the Earth and is key for the processes like photosynthesis, solar energy generation and many more. Sound is also a form of energy that can transmit through solids, liquids and gases. Sound is audible in the range of 20 Hz and 20 kHz.

Light and sound can undergo many phenomena, which we can witness in our daily life. Light is responsible for the blue colour appearance of the sky. Light is also a key factor of bending appearance when an object moves from air to water. A rainbow is an ideal example that is formed by light. The echo is the result of the reflection of sound. The sound felt while striking a tuning fork. SONAR is a technique developed on sound propagation that helps to communicate, navigate, or detect objects on or under the surface of the water. These phenomena are witnessed since light and sound waves can undergo phenomena like reflection, refraction, polarization and interference. Along with these phenomena, light can also undergo diffraction, and scattering.

In this article, let us learn in detail about the interference of waves and their types.

Wave Interference

The interference of waves can be witnessed when two waves travel along with the same medium. This phenomenon occurs when two waves meet or superimpose while travelling. The resultant wave is formed when two waves interfere. The value of the resultant wave is given by the sum of the individual waves.

Interference is of two types:

  1. Constructive Interference
  2. Destructive Interference

Constructive Interference

When two waves travel in the same direction and are in phase with each other, their amplitude gets added, and the resultant wave is obtained. Here, the waves are said to have undergone constructive interference. Upward displacement happens when the waves undergo constructive interference; hence, the upward displacement of the medium is greater than the displacement of the two interfering pulses.

Wave Interference

The constructive interference pattern of the waves is as represented in the figure above. When a crest of one wave meets a crest of another wave of the same frequency, then the resultant amplitude is the sum of the individual amplitudes of the waves. We can also observe that the amplitude of the resultant wave is higher than the waves which undergo interference. Constructive interference occurs when the phase difference between the waves is an even multiple of π (180°).

Example: When we see two speakers right next to each other, we can experience constructive interference when the distance from each speaker to the observer is the same. The path difference must be equal to zero.

Destructive Interference

This kind of wave interference takes place in any location along with the medium when the two waves that interfere with each other have a displacement in the opposite direction. The destructive interference pattern of the waves is shown in the figure above. When a crest of a wave meets a trough of another wave, the waves are said to undergo destructive interference. The sine wave with +1 unit maximum displacement meets a sine wave with -1 unit maximum displacement; destructive interference occurs. The resulting amplitude of the wave, which undergoes destructive interference, is equal to the difference in the individual amplitudes of the waves. This type of interference occurs when the difference is an odd multiple of π.

Read more about the coherent sources and sustained interference.

Stay tuned with BYJU’S to know more about sound waves and light waves. Also learn in detail about interference of waves in an engaging way.

Frequently Asked Questions on light and Interference

1. The speed of a wave is given by which equation?

V=λf.

2. What is the relationship between the time period and frequency?

T= 1/f.

3. What is interference of waves?

The phenomenon that occurs when two waves meet while traveling along the same medium.

4. What is destructive interference?

The wave interference that takes place in any location along the medium when the waves that interfere have a displacement in the opposite direction.

5. Can light waves undergo interference?

Yes.

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