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Light waves of various wavelengths produce distinct hues of light. When different light colors pass over a water droplet, they bend differently, with blue light bending more than red. The bending phenomenon, known as light refraction, effectively divides a single beam of light into the several colored rays of light from which it is formed. As a result, a massive cloud of droplets will divide a sunbeam and curve it into a range, violet and blue on one end and red on the other. It’s how water droplets produce colored light, but soap bubbles do something a little different.
If you’ve ever thrown stones in a quiet lake, you’ve probably noticed ripples spreading out in circles. If you throw two pebbles simultaneously, a meter or two apart, you’ll obtain two pairs of ripples flowing toward each other. The waves overlap when they meet. Some of the waves add up, while others cancel out. This is known as interference. This is called constructive interference; when they neutralize (or subtract), this is called destructive interference. Interference produces a completely new set of waves distinct from those produced by either stone alone. Interference may occur with light waves, which is what happens with colored soap bubbles.
Interference Conditions
Identifying the origins of light is also a significant element in evaluating thin-film interference. A source might be either monochromatic or broadband. Interference patterns emerge as light or dark bands when a monochromatic source is used. The interference patterns emerge as colorful bands due to the utilization of a broadband source.
We’ll look at the key interfering circumstances to better understand the notion.
The kind of reflection experienced by light waves at each border is determined by the refraction indices of the two media.
- Soft reflection:Â No phase shift is noticed when light reflects off material with a lower refractive index.
- Hard reflection occurs when light reflects off a higher refractive index material.
Thin-film Interference Bubble Soap
Light waves flow through the airflow and strike the soap coating as we blow a soap bubble. The refractive index of air is 1 (Nair = 1), but the index of the film is more than 1 (refractive index of film > 1).
On the other contrary, the reflected wave will have a 180° phase change. It takes place at the film’s uppermost point. The shift happens mostly because the air has a lower refractive index than the film.
Furthermore, the light will continue to go from the top air-film contact to the lower film-air interface, where it will be reflected. The phase of the reflected signal is not altered in this case.
Color in a Soap Bubble
Strange things happen when white light strikes a bubble. Keep in mind that light can act like a wave. When light waves strike a bubble, a few of them bounce back off the soap film’s outer surface. Others continue but eventually bounce off the inside of the film. So one set of light rays shines into a bubble, but the other set of light rays emerge. The waves that bounce off the inner film have gone somewhat further than the pulses that bounce off the outer layer when they emerge. As a result, we now have two pairs of light particles that are slightly out of sync. These waves begin to merge like two pairs of droplets on a pond. Some add up, and some cancel out, just like on a pond. The overall result is that some of the colors in the pure white light vanish completely, leaving behind other hues. These are the colors that may be seen in soap bubbles.
Non-Reflecting Films
When light passes from one medium to another, some of the light is diffracted even though the latter is transparent. Non-reflective films are those in which light incident on them (for a specific range of wavelengths) is not reflected.
Non-reflective coatings are designed so that reflected light from the surface interferes negatively. As a result, the intensity of the reflected light will also be zero, and all of the incident light’s energy will be delivered. The destructive interference is created by the reflected light from the film’s two surfaces. As a result, the film has a perfect thickness. Furthermore, a single non-reflective coating does not operate for all light and conceivable incidence angles. It operates for a characteristic wavelength and a specific range of incoming angles.
Conclusion
Making non-reflective coatings is one of the practical uses of the interference phenomena. The bounce from either a lens or a prism can also be reduced to a bare minimum by coating it with a thin layer of the appropriate thickness. Hope this article helps you to understand the topic.
