Interference of light is the phenomenon that causes a reformation of the intensity of light radiations. This mainly happens due to the superposition of two or more light waves. The superposition of two or more waves occurs when the waves propagate in the same medium at the same time and meet each other at the same point. The resultant wave is a combination of all the incident waves. This means that the amplitude of the resultant wave is the algebraic sum of the amplitudes of individual waves.
Types of Interference of Light
The phenomenon of interference of light can be classified into two broad categories:
1. Constructive Interference
The constructive interference of light occurs when the crest of one wave perfectly gets coincided with the crest of the other waves. During constructive interference, the light radiations are in phase with each other, which leads to a significant increase in the intensity of the resultant light.
2. Destructive Interference
The destructive interference of light occurs when the two light waves meet each other out of phase. This means that the intensity of the resultant light gets reduced by a certain amount.
Examples of Interference of Light
1. Blue Morpho Butterfly
A blue morpho butterfly is one of the prominent examples of interference of light in real life. A blue morpho butterfly is typically found in the tropical forests of Latin America. The blue colour of such a butterfly is mainly due to the interference of light and not due to natural pigmentation. The upper surface of the wings of a blue morpho butterfly is made up of nanostructures. When the light falls on the surface of the wings, the blue colour out of the spectrum undergoes a constructive interference and the rest colours tend to encounter destructive interference. This is the reason why only a vibrant blue colour is visible on the surface of the wings.
2. Soap Bubbles
Soap bubbles are yet another example of the interference of light in real life. Soap bubbles are spherical in shape and have a thin transparent layer made up of soap solution. When the white light falls on the surface of the soap bubble and gets reflected from the top and bottom surface of the soap bubble, only a few colours contained by the white light tend to experience constructive interference, while the rest colours undergo destructive interference of light. The colours that encounter constructive interference are visible, while the rest colours get suppressed.
3. Colour Patches on Wet Roads
One can easily observe colour patches formed on the roads during the rainy season. These colour patches on wet roads are basically formed due to the phenomenon of interference of white light. A thin layer of oil, deposited on the surface of the wet road, is primarily responsible for the constructive and destructive interference of the colours contained by the incident white light. When the light is made to strike the surface of the road, it gets reflected by the top and the bottom surface of the oil layer. The colours contained by the light that suffer a constructive interference are easily visible to the observer, while the colours that undergo destructive interference get hindered.
4. Anti-reflective Coating
The anti-reflective coating present on the surface of lenses of the spectacles, camera, etc. is one of the prime applications of interference of light in real life. The main purpose of such anti-reflective coatings is to reduce the intensity of the light falling on the surface of the object. A similar interference phenomenon can also be observed on the surface of the car windows.
5. Oil on the Surface of Water
Oil and water have different chemical and physical properties. The density of oil is comparatively less than the water. This is the reason why the two fluids do not get mixed with each other and oil tends to float on the surface of the water. When a ray of light hits the surface of the oil, it gets reflected by the top and the bottom surface of the layer. This causes the colours contained by the light radiation to undergo constructive as well as destructive interference. The construction interference of colours of the light leads to the formation of a multi-coloured visible pattern on the surface of the oil.
Hologram technology also makes use of interference of light radiations to produce a three-dimensional image of objects in real life.