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I wanna talk a little bit more about reflection and specular and diffuse reflection in particular

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and to start of, I wanna make a minor correction to the last video, and it's actually a pretty interesting

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correction because in this image right here

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I talked about a double reflection

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I talked about the light from the sun hitting this pond

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or specularly reflecting off of the surface of this pond

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and than reflecting off of this paddle to get to our eye

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and when I said where the light ray was passing

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in the last video, I said "it goes from the sun to this point-to this point on the surface

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cause that's where we saw the reflection

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and I said, "than from that point to this point of the paddle

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than to our eye that the correction here

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--and someone pointed this out on the message board and it's a very good catch--

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is that this point is where the light if reflecting to our eye

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so that because we see it, we see the sun there

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so this light ray right here is coming directly to, directly to

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someone's eye-let me draw someone's eye right there

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or our eye, our eye coming straight out of the page

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the light that got reflected here is going to be reflected

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a little bit more shallowly

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so it came from the sun, it came from the sun

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now obviously this won't be exact, but it came from the sun

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it probably had a slightly more shallow (uh uh) angle of incidence

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or angle between the ray and the surface

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and than it would have gotten to

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than it would have gotten to the paddle

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than it would have gotten to the paddle, than it would get to our eye

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and I wanna make clear

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we don't see the sun at the point that it is reflected

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because that light that image of the sun is going to the paddle

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which than goes to our eye

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the point where we see the sun-the reflection of the sun

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that light's going straight into our eye

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it wouldn't have to be reflected by the paddle

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so that was an interesting and good catch when you think about the double reflection

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the other thing I wanna talk about

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is when you have both specular and diffuse reflection happening at the same time

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now, we see this all over the place

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any time you see kind of a shiny object

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something that's not a mirror, but it's a shiny object

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and we see that right here in the apple, just to make this clear

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so you can see, this-this- white part right here, which we've all seen on a nicely waxed apple

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this is, it's like a reflection of the actually light source

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while everywhere else, it's just kind of the color of the apple

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let's think about what's happening here

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so if I were to draw the surface, if I were to draw the surface of the apple

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let me draw it, let me draw it in a neutral color

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so let's say we have the surface of the apple right over here

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we have the surface of the apple right over there

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and than maybe I'll draw it as a slight circle, just so you can appreciate that it's a circular apple

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so the surface of the apple right over here

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you have some light source, so you have some light source

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,so if you have some light source over here

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and it's, and it's emitting light

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so it is emitting light in some direction, onto the surface of the apple

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and what's happening on the surface of the apple, there's

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there's a couple of things that's happening

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you're having some of this light is reflecting specularly

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or, another way of thinking about it is it's maintaining the image, a little of it, but not all of it

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so let me just draw it, so if you're coming in at that incident angle

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you're going to leave at that reflected angle

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and if you came in at this incident angle, you're going to leave at that reflected angle

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and if you came in at this incident angle, going to leave at that reflected angle

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and I'm doing dotted lines to show that it's not all of the light that's getting reflected that way

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only some of the light is getting that specular reflection

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,but if someone, if this light were to be reaching your eye

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if, let me draw a proper face, so let's say this is someone's face right here that someone's, that's there ear, or there hair

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that's there eyebrows, that's there moustacche

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and, I think you get the general idea

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so this person will see a reasonably good version of the light source

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which we see right over here, but what's going on the rest of the apple

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or even over here, so some of the light is reflecting specularly

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it's kind of maintaining the image of the light source

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although that's getting distorted a little bit

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but the rest of the light, the rest of the light

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and let me be clear here- the rest of-some of it is being absorbed

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some of it is being absorbed by the actual surface of the apple

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but the rest of it reflecting red light, what we see is actually what the light, apple does not absorb

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what the apple is reflecting, but that red light that mainly red

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I mean it's a bunch of different shades over here

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is reflecting diffusely, so that pure light comes in here, some of the pure light get reflected specularly

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or kind of purely maintaining the image, but some of it, because the surface of the apple isn't smooth

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is going in all sorts of directions, so of it's going like that, some of it's going like that

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some of it's going like that, and that's happening at every

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at every point on the apple, so that light source

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let me draw more of the light source, so rays coming in, and rays coming in from our light source

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but every point of the apple is also having this diffuse reflection

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which is reflecting only the red part of the spectrum, it's absorbing all of the other parts of the spectrum

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and, so what you see is, that point where you're getting the pure specular

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the pure specular reflections, that's the point that looks shiny

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where you can kind of see the light source

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and from every other point on the apple, where only this guy right here's only getting the diffuse red light

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and that's why, if you move the apple, or actually even better, if you move where you're looking at the apple

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that, point of reflection's gonna look, like if I start looking at it from this direction

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I'm gonna get a different point of reflection, cause I'm gonna start seeing the light

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though let's see, let's say that someone's eyeball is right, actually right over here

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so that's their eyebrows, that's their eyeball, that's their nose, you get the general idea

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so let's say that this person, let's say that this person, that's their ear

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there, I don't wanna get too involved in the drawing

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so let's say that this person is looking at this supper ginormous apple now relatively to him

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he is not gonna see this white spot there

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he is gonna see the white spot on the point where it looks like

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where he's getting the right angle, where, where the rays are coming in

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let me do it in a different color

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so let's say, let's say the light source is above us

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so the light source is coming straight down

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is coming straight down to the apple and than if it's the right angle

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if the angle of incidence and the angle of reflection relative to the surface of the apple

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and we can draw that out, we can draw it perpendicular to the surface of the apple

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this is the angle of incidence, this is the angle of reflection

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so those points, at that point right there he's getting a little bit

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and I should draw a dotted line

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he's getting a little bit of the, of the specular reflection, but from every other point

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so for every other point on the apple, so over here, the specular reflection would go that way

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not to his eyes, or it would go that way, not to his eyes

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but from those points you also have some of the diffuse reflections

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and some of that is going to his eye in terms of red

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the red part of the frequency is getting to his eye from all of these other random directions

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and that's why this guy over here, he would see this, this reflection

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he would see this reflection rougly over here, and all of this other part of the apple would look red

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and we, since we're on this side of the apple, we see the reflection point

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the light is coming straight down from our light source bouncing right here

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than coming straight out towards our eye

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coming down, and than reflecting, coming straight out towards our eye

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it's also coming down on these other points, but those other points are going straight out

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to some place where our eye isn't, instead we're just seeing, we're just seeing the diffuse part

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that is actually coming to our eye

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anyway, hopefully you found that a little bit more, um, filled in a couple of the gaps of the last video