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Course: Middle school physics - NGSS > Unit 4
Lesson 3: Transmission and refractionRefraction and frequency
Waves will refract when they travel from one material into another. Light travels in straight lines until it hits a prism, where it bends and spreads out into different colors. This bending, called refraction, happens when light moves from one transparent medium to another. Depending on the frequency of the wave, it could refract more or less. That's why rainbows form and why images in water can look distorted. Created by Sal Khan.
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I have a lot of questions, but I’d be happy is someone could just answer one! :)
1. When we say a prism, do we mean a triangular prism made of glass, or just a flat piece of glass shaped like a triangle?
2. When Khan says this refraction will only happen when the light hits the prism at an angle, what does he mean? Does he mean it will happen when it hits the angle of the triangle? Or when the light in reference to the glass is at an angle? I don’t understand.
3. What is refraction in the end? The act of the light bending when hitting glass prisms? Or just the act of light bending. If it’s the second answer, what are some other instances of refraction?(16 votes)
2. It means it hits an angle of the glass triangle.(6 votes)
At0:03the video says that light can go through a vacuum. But why can light, and not any other type of wave go through a vacuum?(4 votes)
Sound can't pass through vacuum beacause it needs air but there is no air vacuum so sound waves can't pass
i hope you understood a little bit of something!(6 votes)
- when he said "vacuum" does he mean a vacuum or something eles like space?(3 votes)
space is a vacuum because it has practically no atoms(3 votes)
Pink Floyd Album Cover(4 votes)
What happens if light goes through two consecutive prisms?(2 votes)
One of two things determined on how you place them. The light could get spread even farther apart, or they could combine back into white light.(2 votes)
- how come light can light go through a vacuum, but not any other type of wave?(2 votes)
Because light is an electromagnetic wave, but the "other waves" you're talking about are mechanical waves. Electromagnetic waves don't need a medium to travel through, but mechanical waves can only be transmitted through a medium.
Light isn't the only wave that can travel through a vacuum - x-rays, gamma rays, and ultraviolet radiation are all electromagnetic waves.(2 votes)
- If the colors white and black both have all the different colors/wavelengths, then how do we tell them apart?(2 votes)
- White light contains all of the light frequencies, while an object with the color black is a mix of all of the solid colors. So light as black is nothing, and white of light is all. And black as paint is everything, and white as paint is nothing. (this the best way how to explain it, sorry it's confusing).(2 votes)
What happens if light goes through two consecutive prisms?(2 votes)- One of two things determined on how you place them. The light could get spread even farther apart, or they could combine back into white light.(1 vote)
- Once When I was washing The water was a rainbow(2 votes)
Isn't the light traveling through a medium when it travels the prism? Light usually travels through vacuums but here it can travel through mediums as well. So can light travel through transparent/translucent mediums?(1 vote)
Yes, light can travel through many mediums. We often talk about the speed of light through a vacuum because that speed is constant. In our everyday lives, though, light isn’t usually traveling through a vacuum. Light does travel slightly more slowly through air than through a vacuum, and it’s even slower in water.(2 votes)
0:03Video transcript
- [Instructor] When light is
going through a uniform medium, like the air, or as we know, light
can go through a vacuum, so nothing at all, we imagine it going in a straight line, but we see something really
interesting happening here. When it hits this glass prism, I know it just looks like
a gray triangle to you, but imagine it as a
triangular piece of glass, and it's hitting it at an angle. What this animation shows us is that the path of the
light actually gets bent, and not only does it get bent, but the different frequencies of the light get bent by different amounts. Now, if you were to look
at this with your eyes, you wouldn't be able to
see the actual waves, like we're seeing in this
diagram right over here. You would just see how
your brain or how your mind perceives the various frequencies, and that's why they made
the higher frequencies here more like a violet or a purple color, and that's why they made
the lower frequencies here more of a red color, because that's how your brain or your mind would perceive them. But you can see as this light goes from, let's say the vacuum to this prism, to this crystal or this glass, the high-frequency light gets bent more, and the low-frequency light,
which still gets bent, gets bent less, and then that essentially spreads out all of the wavelengths. When we have white light, it has all of the visible
wavelengths in it, but when it hits a prism like this, if you imagine a triangular
piece of glass or crystal and it hits it at an angle, well, then the different
wavelengths spread out, and if you were to put
a piece of paper here, you would see a rainbow, and that's actually how
rainbows are formed. A bunch of water particles
in the air refract light exactly like this. This process of when light goes from one transparent medium
to another, or a vacuum, to some other medium that it can travel through
that's transparent, if it hits it in an
angle, it can get bent, which is what we called refraction. This is why when you
look at a cup of water or at a pool at an angle, you're not seeing
directly through the pool. The image gets distorted.