00:02
All right, so your questions are all about ray diagrams and the lens equations.
00:09
So i'm going to show you how to draw a ray diagram first.
00:14
I don't know your do value or your object's distance.
00:19
It's been cut off on your screen capture, so i'm just going to leave that as do.
00:24
The focal point is 25 on this lens, so f1 and f2 are 25 and negative 25.
00:32
H .o, the height of the image, or excuse me, height of the object is 10.
00:38
And if we do a tracing of this, we're going to get what looks like a converging ray diagram on the right side, where d .i.
00:52
Will be and h .i.
00:54
Will also be.
00:55
Now, i can't know for sure what those values are because i can't tell what do is.
01:01
But if i use this equation up at the top right, i can calculate that.
01:06
So that's one of the questions that they're asking is, how do you find do? so the ray diagram, i made three lines.
01:14
The green line is going to start by being parallel to the center line.
01:20
My center line is this black.
01:23
It's going to come to the lens location, and then it's going to bend towards the focal point two and pass through that to the other side.
01:32
Side.
01:33
Now, the same will happen with the purple line.
01:36
I'll make that one second, and i will pass through the front focal point and come back out parallel to the center line.
01:46
Those two green and purple lines are going to intersect, and then i'm going to double check it with the third line, which is going to be the top of the object through the center line where the lens is located.
02:00
And that's going to connect all three of those lines to a point.
02:04
And where that connection is occurring is where the image will form.
02:08
So i drew a red arrow downwards because it's upside down.
02:14
And it's a little bit larger than the original object.
02:17
So i don't know what h -i and d -i are, but i can calculate them if i knew where d -o was on this.
02:24
So in summary, to find a rate or to create a ray tracing diagram, you start with a black center line.
02:32
Mark out the f1 and f2 for the lens and where the do is, and then draw a red arrow or some colored arrow representing your object to the correct height.
02:47
And then once you have that, you can start making the three lines, the green, the purple, and the orange lines.
02:54
Where they intersect is where the image will form.
03:00
Now, to find the actual value of something besides using a sketch from a really, diagram, i can use this equation, 1 over f equals 1 over the i plus 1 over do.
03:14
So let's imagine that the do here is a value of 035, 35 centimeters using your lens here with a focal point of 25.
03:34
So if i use 1 over f, which is 1 over 25, it's a converging lens.
03:42
So we can use positive 25, 1 over sum value d .i plus 1 over 35.
03:52
So if i use algebra here, i can find what d .i is by taking 1 25th minus 1 .35th, whatever that sum is.
04:07
Inverse that or take it to the negative one power and that would tell me d .i.
04:12
So that's kind of how you would do this problem.
04:14
I just don't have the exact value you used in your homework problem.
04:22
But this is an example of how you would do it.
04:29
So if i put this into the calculator, 1 divided by 25 minus 1 divided by 35, and then i'm going to inverse that answer.
04:40
I get 87 .5.
04:41
That's where the image is going to form for this scenario that i just made up.
04:49
All right.
04:49
So the last question is, what will happen if we have a second lens? now, i'm going to make a new arrow here.
04:59
I'll make it red again, just like before...