All about light
The human eye is a fascinating thing. Windows to the brain, each image you see, instantly clicking into your memory, understanding what you see through your eyes, is what is around you. But have you ever wondered how it all works? Light. Light is the answer to that question. The simple word is a marvelous thing that allows you to absorb your surroundings. Without light, all there is darkness. Complete and utter darkness. You wouldn't be able to see a single movement or anything, in fact without it. So how does it all work? How does light allow us to see things? - QueenCleoP 04/09/2017
How does light work?
Light is at once both obvious and mysterious. We are bathed in yellow warmth every day and deter the darkness with incandescent and fluorescent bulbs. Light travels in waves called transverse waves which is faster than sound. They travel in straight lines and unlike sound waves, light waves can travel through a vacuum (empty space). They do not need a substance to travel through, but they can travel through transparent and translucent substances. Light travels extremely quickly. Its maximum speed is approximately 300,000,000 m/s, when it travels through a vacuum. The very large difference between the speed of light in air (almost 300,000,000 m/s) and the speed of sound in air (343 m/s), this explains why you see lightning before you hear it as the same goes to fireworks.
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Reflection
When light reaches a mirror, it reflects off the surface of the mirror. The law of reflection states that the angle of incidence equals the angle of reflection, i = r. It works for any angle for example the angle of reflection is 30° if the angle of incidence is 30° and the angle of reflection is 90° if the angle of incidence is 90°. When you think of reflection, think about mirrors. They reflect all of the light. That is the reason you can see yourself. Even the ocean reflects light, just not all of it. If you are above the ocean, you can't see the reflection that well, but when you are at an angle, look closely; you can see a reflection of the sky. So the ocean only has partial reflectivity. Reflection can happen in two quite different ways. If you have a smooth, highly polished surface and you shine a narrow beam of light at it, you get a narrow beam of light reflected back off it. This is called specular reflection and it's what happens if you shine a flashlight or laser into a mirror: you get a well-defined beam of light bouncing back towards you. Most objects aren't smooth and highly polished: they're quite rough. So, when you shine light onto them, it's scattered all over the place. This is called diffuse reflection and it's how we see most objects around us as they scatter the light falling on them.
If you can see your face in something, it's specular reflection; if you can't see your face, it's diffuse reflection. Polish up a teaspoon and you can see your face quite clearly. But if the spoon is dirty, all the bits of dirt and dust are scattering light in all directions and your face disappears
If you can see your face in something, it's specular reflection; if you can't see your face, it's diffuse reflection. Polish up a teaspoon and you can see your face quite clearly. But if the spoon is dirty, all the bits of dirt and dust are scattering light in all directions and your face disappears
Refraction
Light waves travel in straight lines through empty space (a vacuum), but more interesting things happen to them when they travel through other materials especially when they move from one material to another. That's not unusual: we do the same thing ourselves.
Have you noticed how your body slows down when you try to walk through water? You go racing down the beach at top speed but, as soon as you hit the sea, you slow right down. No matter how hard you try, you cannot run as quickly through water as through air. The dense liquid is harder to push out of the way, so it slows you down. Exactly the same thing happens to light if you shine it into water, glass, plastic or another more dense material: it slows down quite dramatically. This tends to make light waves bend, something we usually call refraction. |
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We see the world what way?
Your eyes actually perceive the world upside down (before your brain crunches the data, anyway). That's due to the process of refraction through a convex lens—that is, the bending of light through a surface that bows outward in the middle, like your eye or a camera lens. In the 17th century, French philosopher and scientist René Descartes proved this by replacing the retina of a dead cow's eye with a screen. The screen showed a flipped version of the scene in front of the eye.So why do we see the world right-side up while experts think newborns see it upside-down? Brain development. Our brains have learned to automatically flip the images that hit our retinas so we perceive our reality right side up. Babies' brains haven't quite learned to do that yet, and until they do, it is believed that the babies live in an "upside-down" world.
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Spectrum of light
White light can be split up into a spectrum of many different colors and visible light is just part of a continuous spectrum of electromagnetic radiation. Using a prism, you can split up white light to form a spectrum. (A prism is a block of glass with a triangular cross-section.) The light waves are refracted as they enter and leave the prism. The shorter the wavelength of the light, the more it is refracted. As a result, red light is refracted the least and violet light is refracted the most, causing the coloured light to spread out to form a spectrum.
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