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What is light?
Most people think Light as something that comes from the sun and allows us to see. But light is actually much more than that. It is a form of energy that travels through the air, and it is made up of tiny particles called photons.
Light travels in straight line until it hits an object. When it hits an object, it can be reflected, refracted, or absorbed. Reflection is when light hits an object and bounces off. This is what happens when you see your reflection in a mirror. Refraction is when light changes direction as it passes through an object. This is what happens when you see a pencil in a glass of water. Absorption is when light hits an object and is absorbed by it.
How does light travel?
Most of us take light for granted. We flip a switch and a room is filled with light. We step outside and are blinded by the sun. But what is light, really? And how does it travel from its source to our eyes?
Light is actually a type of energy called electromagnetic radiation. It travels through the air (or other mediums, like water or glass) as a wave. But unlike water waves, which need molecules to travel through, light waves do not need anything to travel through — they can move through a vacuum.
How does light travel? When light waves leave a source (like the sun or a light bulb), they vibrate in all different directions. But when these waves hit an object (like your eye), they bounce off in a specific direction. That’s how we are able to see things!
The speed of light is always the same — about 186,000 miles per second (300,000 kilometers per second). But the wavelength (the distance between each wave) can be different. Waves with shorter wavelengths are called gamma rays, while those with longer wavelengths are called radio waves. Visible light falls somewhere in between these two extremes.
The speed of light
The speed of light in a vacuum is 299,792,458 metres per second (about 186,282 miles per second). It is the fastest speed at which energy and information can travel.
Light travels as a wave and as a particle (called a photon). As a wave, it can travel through any medium – even through a vacuum. As a particle, it travels only through space where there is something for it to interact with – like other particles or atoms.
How fast light travel in different materials? It depends on how much the material slows it down. The speed of light slows down when it enters certain materials – like water or glass.
The amount that the speed of light slows down in different materials is called the refractive index.
How light travel from a source?
Most people think of light as traveling in a straight line. However, this is not always the case. Light can bend, or refract, as it passes through different materials. This happens because light travels at different speeds in different materials.
For example, light travels more slowly through water than it does through air. This is why objects look bent when you look at them through water. The speed of light also changes when it passes from one material to another, such as from glass to air. When this happens, the light bends because the part of the light wave that travels fastest (the crest) slows down first, then the rest of the wave catches up with it.
The amount that light bends depends on the difference in speed between the two materials and on the angle at which the light hits the surface between them.
The light spectrum
There is a wide range of colors in the light spectrum, from red to violet. Each color has a different wavelength, and when all the colors are combined, they create white light. Sunlight is an example of white light.
Light waves are produced when electrons in atoms get excited and release energy. This energy travels through space in the form of waves. The distance between the peaks of two successive waves is called the wavelength. The shorter the wavelength, the higher the energy of the light wave.
Visible light makes up a tiny part of the electromagnetic spectrum. It is the part that our eyes can see. But there are other types of electromagnetic radiation that we can’t see, such as radio waves, microwaves, X-rays, and gamma rays.
What is a light source?
A light source is anything that emits light.
Natural sources of light include the sun, stars, and fire.
Man-made sources of light include lightbulbs and lamps.
Light is made up of tiny particles called photons. When a source of light is turned on, the photons start moving away from the source in a straight line.
The sun as a light source
The sun emits a type of electromagnetic radiation calledvisible light. This radiation travels through the vacuum ofspace at a speed of about 300,000 kilometers per second.
When this light reaches Earth, it is scattered in alldirections by the molecules in the atmosphere. Some of thislight strikes the ground and is then scattered upward by thesurfaces of objects on the ground, such as buildings, trees,and dirt. Finally, some of this light enters your eyes, whereeach light-sensitive retina detects and converts it into neuralimpulses that are relayed to your brain.
Artificial light sources
Most artificial light sources emit light in a cone, with the light rays traveling parallel to one another. The angle of the cone depends on the type of light source. For example, a standard incandescent light bulb has a cone angle of around 15 degrees, while a spotlight can have a cone angle of just 5 degrees.
The size of the light source also affects how the light rays travel. A small light source, such as a LED, will emit light in a very focused beam. A larger light source, such as a fluorescent tube, will emit light over a wider area.
Reflection and refraction
When light waves strike an object, they can be reflected, refracted, or absorbed.
Reflection is when light waves bounce off an object. Mirrors reflect light in a regular pattern so that we see a clear image. Other surfaces reflect light in a diffuse pattern so that we see a scattered image.
Refraction is when light waves bend as they pass through an object. This happens because light travels at different speeds in different materials. For example, light bends when it passes from air into water. This is why a stick looks bent when you hold it in the water.
The human eye and light
Light from a source such as the sun or a light bulb travels in a straight line until it hits an object. The object will then reflect, refract, or absorb the light. Our eyes only see the light that is reflected off of objects.
When light reflects off of an object, we see the color of that object because each color reflects a different wavelength of light. White objects reflect all colors of light equally, while black objects absorb all colors of light. Objects that are red reflect red light and absorb all other colors.
When light passes through an object, it is either refracted or absorbed. Clear objects like glass or water will refract light while dark objects like coal will absorb it. If an object is transparent, like a window, the light will pass straight through it.