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December 14th, 2014, 05:02 PM   #1
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if light cannot bend then how refraction & reflection of light works?

if light cannot bend then how refraction & reflection of light are working?
is it still mystery or any other theory is there for this?
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December 14th, 2014, 05:48 PM   #2
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Light can bend! This was one of the predictions that validated relativity. Well, strictly speaking it's the space that curves rather than the light, but the effect is the same.

Reflection is basically the same as bouncing balls off a wall, although here the balls would be photons.

Refraction is caused by the different velocity of waves in two media.
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December 14th, 2014, 06:16 PM   #3
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Quote:
Originally Posted by v8archie View Post
the space that curves rather than the light,
sorry My question is regarding light bend, so i don't know why you mention "space" in your reply, i am not asking about space bends or not.
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December 14th, 2014, 06:21 PM   #4
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Quote:
Originally Posted by Ganesh Ujwal View Post
sorry My question is regarding light bend, so i don't know why you mention "space" in your reply, i am not asking about space bends or not.
Read that post again carefully.
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December 14th, 2014, 06:25 PM   #5
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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.

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.

How refraction works :
Refraction of laser beams inside crystals
Photo: Laser beams bending (refracting) through a crystal. Photo by Warren Gretz courtesy of US Department of Energy/National Renewable Energy Laboratory (DOE/NREL).

You've probably noticed that water can bend light. You can see this for yourself by putting a straw in a glass of water. Notice how the straw appears to kink at the point where the water meets the air above it. The bending happens not in the water itself but at the junction of the air and the water. You can see the same thing happening in this photo of laser light beams shining between two crystals. As the beams cross the junction, they bend quite noticeably.

Artwork explaining how refraction (the bending of light) happens when light rays slow down

Why does this happen? You may have learned that the speed of light is always the same, but that's only true when light travels in a vacuum. In fact, light travels more slowly in some materials than others. It goes more slowly in water than in air. Or, to put it another way, light slows down when it moves from air to water and it speeds up when it moves from water to air. This is what causes the straw to look bent. Let's look into this a bit more closely.

Imagine a light ray zooming along through the air at an angle to some water. Now imagine that the light ray is actually a line of people swimming along in formation, side-by-side, through the air. The swimmers on one side are going to enter the water more quickly than the swimmers on the other side and, as they do so, they are going to slow down—because people move more slowly in water than in air. That means the whole line is going to start slowing down, beginning with the swimmers at one side and ending with the swimmers on the other side some time later. That's going to cause the entire line to bend at an angle. This is exactly how light behaves when it enters water—and why water makes a straw look bent.

Last edited by Prakhar; December 14th, 2014 at 06:28 PM.
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