How does light travel? It’s a question that has puzzled scientists for centuries. But now, thanks to the latest research, we may finally have an answer.
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How does light travel?
Light travels in a straight line until it hits an object. Then, it either bounces off the object or is absorbed by it. When light bounces off an object, we see the object because our eyes receive the light that was reflected by the object.
The speed of light
In a perfect vacuum, light always travels at the same speed. This is the highest speed that anything can travel. The speed of light in a vacuum is about 186,282 miles per second, or about 300 million meters per second. It’s fast!
Light doesn’t always travel at this speed. It slows down when it passes through different materials. For example, it travels more slowly through water than it does through air. The speed of light also changes depending on the type of material it is passing through. It passes more slowly through glass than it does through air.
You might be wondering how we know the speed of light if it is so fast that we can’t see it happening. Scientists have come up with some clever ways to measure the speed of light. One way is to use a device called a Michelson interferometer. This device splits a beam of light into two beams that travel in different directions. The beams are then reflected back and allowed to recombine. By measuring the interference pattern that is created, scientists can calculate the speed of light.
How light travels through different mediums
When light travelling through different mediums, it may be refracted, reflected, or absorbed. The type of interaction that light has with the molecules of the medium determine how the light will be affected.
Refraction is when light changes directions as it passes through a medium. This occurs because the velocity of light changes as it goes from one medium to another. For example, when light moves from air into water, it slows down and bends.
Reflection occurs when light bounces off of a surface. This can happen when light hits a mirror, or when it hits a rough surface like concrete. The angle at which the light hits the surface will determine how much reflection occurs.
Absorption is when light is absorbed by the molecules in a medium. This happens when light hits a dark colored object like black paint. The darker the object, the more absorption that will occur.
The reflection of light
Light is a type of energy that travels through the air and is reflected off surfaces. When light hits an object, some of the light is reflected off the surface of the object. The amount of light that is reflected depends on the surface of the object. For example, a smooth, shiny surface will reflect more light than a dull, rough surface.
The refraction of light
When a light wave strikes an object, some of the light is reflected off the surface while the rest of the light penetrates the surface and is eventually absorbed. The “color” that we see is a result of which wavelengths are reflected back to our eyes. For example, a red apple looks red because all of the other colors (or wavelengths) are absorbed except for red, which is reflected.
When light passes from one medium to another (for example, from air into water), it bends, or refracts. This occurs because waves travel faster in some mediums than others. The amount of bending depends on the difference in speed between the two mediums and the wavelength of the light.
The dispersion of light
Dispersion is the process by which light is broken up into its constituent colors. When white light shines on a prism, for example, the different wavelengths of light are bent by different amounts and spread out into a spectrum of colors. This is because each color component of white light (red, orange, yellow, green, blue, indigo, and violet) has a different wavelength and travels at a different speed in glass.
The amount by which each color is bent (the refractive index) depends on the wavelength of the light. Red light, with its long wavelength, is refracted less than violet light, with its shorter wavelength. This difference in bending produces the visible spectrum — an array of colors that we see when light is dispersed.
The interference of light
At its simplest, light can be described as a stream of photons traveling through the vacuum of space. However, when this stream of photons encounters matter, it starts to behave in strange and wonderful ways. One of the most intriguing behaviors of light is interference — the ability of light waves to cancel each other out or amplify each other.
When two waves meet, they interact with each other — a process known as superposition. The net effect of this interaction is determined by the difference in their amplitudes, or heights. If the two waves have identical amplitudes, they will cancel each other out completely, producing what is known as destructive interference.
Conversely, if the two waves have opposite amplitudes — one high and one low — they will amplify each other, producing what is known as constructive interference. The net effect of constructive interference is a wave with an amplitude that is the sum of the amplitudes of the individual waves.
Interference can also occur when a single light wave encounters itself. This happens when a wave is reflected off a mirror or bounces off a boundary between two different materials. When this happens, the wave effectively splits in two and travels off in different directions. These two waves will eventually meet up again and interfere with each other — an effect known as self-interference.
Self-interference can be constructive or destructive depending on the relative phase shift between the two waves. If the two waves are exactly in phase — that is, if they have identical amplitudes and wavelengths — then they will undergo constructive interference and produce a wave with twice the amplitude of the individual waves.
If, on the other hand, the two waves are exactly out of phase — that is, if one has an amplitude that is precisely equal to and opposite of the other — then they will undergo destructive interference and produce a wave with zero amplitude.
8 ) The diffraction of light
When a light wave meets an obstacle, it is bent around the obstacle. This is called diffraction. The spread of light around an obstacle is an example of diffraction (Figure 8).
The amount of diffraction that occurs depends on the wavelength of the light and the size of the obstacle. For example, blue light (which has a shorter wavelength) is diffracted more than red light (which has a longer wavelength) when both colours pass through a small hole.
The polarization of light
Light is an electromagnetic wave, and as such, it is polarized. This means that the wave oscillates in a particular direction, and this direction is perpendicular to the direction of travel. The polarization of light can be explained by its wave nature: the wavefronts of light are always perpendicular to the direction of propagation.
When light waves reflect off of certain surfaces, they become polarized. This happens because the reflecting surface only reflects a portion of the wavefront, and the reflected waves are out of phase with the incident waves. The net effect is that the reflected waves cancel out except for the component that is perpendicular to the reflecting surface.
Some materials, such as Polaroid sunglasses, can selectively absorb or reflect light depending on its polarization. These materials are said to be “polarizing.” By wearing Polaroid sunglasses, you can reduce the amount of glare from reflections off of surfaces such as water or pavement.
The scattering of light
When light waves hit an object, they can be scattered in many different directions. This process is called scattering. The size and shape of the object determine how much light is scattered and in which direction it scatters.
One type of scattering is called Rayleigh scattering. It occurs when the objects that the light waves hit are very small, such as particles of dust or pollen in the air. The Rayleigh scattering of sunlight is what makes the sky look blue.
Another type of scattering is called Mie scattering. It occurs when the objects that the light waves hit are larger, such as water droplets or pieces of glass. The Mie scattering of sunlight is what makes the sky look white when there are clouds in it.