I wanna talk a little bit more about reflection and specular and diffuse reflection in particular
and to start of, I wanna make a minor correction to the last video, and it's actually a pretty interesting
correction because in this image right here
I talked about a double reflection
I talked about the light from the sun hitting this pond
or specularly reflecting off of the surface of this pond
and than reflecting off of this paddle to get to our eye
and when I said where the light ray was passing
in the last video, I said "it goes from the sun to this point-to this point on the surface
cause that's where we saw the reflection
and I said, "than from that point to this point of the paddle
than to our eye that the correction here
--and someone pointed this out on the message board and it's a very good catch--
is that this point is where the light if reflecting to our eye
so that because we see it, we see the sun there
so this light ray right here is coming directly to, directly to
someone's eye-let me draw someone's eye right there
or our eye, our eye coming straight out of the page
the light that got reflected here is going to be reflected
a little bit more shallowly
so it came from the sun, it came from the sun
now obviously this won't be exact, but it came from the sun
it probably had a slightly more shallow (uh uh) angle of incidence
or angle between the ray and the surface
and than it would have gotten to
than it would have gotten to the paddle
than it would have gotten to the paddle, than it would get to our eye
and I wanna make clear
we don't see the sun at the point that it is reflected
because that light that image of the sun is going to the paddle
which than goes to our eye
the point where we see the sun-the reflection of the sun
that light's going straight into our eye
it wouldn't have to be reflected by the paddle
so that was an interesting and good catch when you think about the double reflection
the other thing I wanna talk about
is when you have both specular and diffuse reflection happening at the same time
now, we see this all over the place
any time you see kind of a shiny object
something that's not a mirror, but it's a shiny object
and we see that right here in the apple, just to make this clear
so you can see, this-this- white part right here, which we've all seen on a nicely waxed apple
this is, it's like a reflection of the actually light source
while everywhere else, it's just kind of the color of the apple
let's think about what's happening here
so if I were to draw the surface, if I were to draw the surface of the apple
let me draw it, let me draw it in a neutral color
so let's say we have the surface of the apple right over here
we have the surface of the apple right over there
and than maybe I'll draw it as a slight circle, just so you can appreciate that it's a circular apple
so the surface of the apple right over here
you have some light source, so you have some light source
,so if you have some light source over here
and it's, and it's emitting light
so it is emitting light in some direction, onto the surface of the apple
and what's happening on the surface of the apple, there's
there's a couple of things that's happening
you're having some of this light is reflecting specularly
or, another way of thinking about it is it's maintaining the image, a little of it, but not all of it
so let me just draw it, so if you're coming in at that incident angle
you're going to leave at that reflected angle
and if you came in at this incident angle, you're going to leave at that reflected angle
and if you came in at this incident angle, going to leave at that reflected angle
and I'm doing dotted lines to show that it's not all of the light that's getting reflected that way
only some of the light is getting that specular reflection
,but if someone, if this light were to be reaching your eye
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
that's there eyebrows, that's there moustacche
and, I think you get the general idea
so this person will see a reasonably good version of the light source
which we see right over here, but what's going on the rest of the apple
or even over here, so some of the light is reflecting specularly
it's kind of maintaining the image of the light source
although that's getting distorted a little bit
but the rest of the light, the rest of the light
and let me be clear here- the rest of-some of it is being absorbed
some of it is being absorbed by the actual surface of the apple
but the rest of it reflecting red light, what we see is actually what the light, apple does not absorb
what the apple is reflecting, but that red light that mainly red
I mean it's a bunch of different shades over here
is reflecting diffusely, so that pure light comes in here, some of the pure light get reflected specularly
or kind of purely maintaining the image, but some of it, because the surface of the apple isn't smooth
is going in all sorts of directions, so of it's going like that, some of it's going like that
some of it's going like that, and that's happening at every
at every point on the apple, so that light source
let me draw more of the light source, so rays coming in, and rays coming in from our light source
but every point of the apple is also having this diffuse reflection
which is reflecting only the red part of the spectrum, it's absorbing all of the other parts of the spectrum
and, so what you see is, that point where you're getting the pure specular
the pure specular reflections, that's the point that looks shiny
where you can kind of see the light source
and from every other point on the apple, where only this guy right here's only getting the diffuse red light
and that's why, if you move the apple, or actually even better, if you move where you're looking at the apple
that, point of reflection's gonna look, like if I start looking at it from this direction
I'm gonna get a different point of reflection, cause I'm gonna start seeing the light
though let's see, let's say that someone's eyeball is right, actually right over here
so that's their eyebrows, that's their eyeball, that's their nose, you get the general idea
so let's say that this person, let's say that this person, that's their ear
there, I don't wanna get too involved in the drawing
so let's say that this person is looking at this supper ginormous apple now relatively to him
he is not gonna see this white spot there
he is gonna see the white spot on the point where it looks like
where he's getting the right angle, where, where the rays are coming in
let me do it in a different color
so let's say, let's say the light source is above us
so the light source is coming straight down
is coming straight down to the apple and than if it's the right angle
if the angle of incidence and the angle of reflection relative to the surface of the apple
and we can draw that out, we can draw it perpendicular to the surface of the apple
this is the angle of incidence, this is the angle of reflection
so those points, at that point right there he's getting a little bit
and I should draw a dotted line
he's getting a little bit of the, of the specular reflection, but from every other point
so for every other point on the apple, so over here, the specular reflection would go that way
not to his eyes, or it would go that way, not to his eyes
but from those points you also have some of the diffuse reflections
and some of that is going to his eye in terms of red
the red part of the frequency is getting to his eye from all of these other random directions
and that's why this guy over here, he would see this, this reflection
he would see this reflection rougly over here, and all of this other part of the apple would look red
and we, since we're on this side of the apple, we see the reflection point
the light is coming straight down from our light source bouncing right here
than coming straight out towards our eye
coming down, and than reflecting, coming straight out towards our eye
it's also coming down on these other points, but those other points are going straight out
to some place where our eye isn't, instead we're just seeing, we're just seeing the diffuse part
that is actually coming to our eye
anyway, hopefully you found that a little bit more, um, filled in a couple of the gaps of the last video