Multiple lens systems | Geometric optics | Physics | Khan Academy

Some examples of using the thin lens equation with multiple lenses. Created by David SantoPietro.

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[Milsap]

This guy is good. Khan academy needs more people like him.

[lightwing]

This video was the best explanation of a multi-lens system I have found thus far.

[miriammadry]

Would you guys consider doing more complex optics videos specifically covering Gaussian lens systems??

[jamesratnavale]

What a wonderful video! Excellent explanation, I would rate this as A+ standard

[aeebeecee]

thin_lens_formula:
image.distance = focal_length * object.distance / (object.distance - focal_length);
object.distance = focal_length * image.distance / (image.distance - focal_length);
focal_length = image.distance * object.distance / (image.distance + object.distance);
magnification_formula:
magnification = -image.distance / object.distance;
magnification = image.height / object.height;
total_magnification_formula:
for (i = 1; i < total, ++i)
magnification[0] *= magnification[i];

# License: CC BY-SA 4.0 or later, AGPL V3.0 or later #

[lakshyasingh]

Hi you explained nicely but 2:43 it u (object distance ) will be negative because according to sign convention of lenses, all distances are taken to be positive when they are in the direction of the incident ray.

[sarthaksharma]

love you khan academy, you are the best of best, thanks and keep making such aha moment videos😉😉😉

[huynguyenanh]

Thanks, it's very clear and easy to follow along!

[lisasolomey]

Thank you so much! You are an amazing teacher.

[yoojinyoung]

if di is negative (-6cm from the calculation) shouldn't it be on the same side of the eye based on your explanation? I get that it will be on the left side of the second lens because the focal length is -10 cm, but following your explanation made me little bit confused.

[j.a.]

at 8:45 in the "Thin lens equation and problem solving" video, David, says " -di = non inverted and +di = inverted; however, in this video at 12:16, he draws the image as inverted, even though he got -di. Why is this? Is this just a "special case" with multiple lenses?

[doilangtu]

tysm u saved my final exam for tomorrow

[lakshyasingh]

6:20 on the concave lens that image distance would be positive (sign convention) you may Google and check

[CrystinexX]

thank you so very much for this explanaiton, it really helps a lot ! (also your voice is really nice to listen to :D)

[ptsimonse]

What if the 2nd lens is closer to the 1st lens than the 1st lens' focal length? e.g. if the 2nd convex lens is 2.5 cm away from the 1st convex lens and both have focal lengths of 5 cm?

[guptak]

What do if the image distance of convex lens is greater than distance BTW lenses

[AnasKhan-eoxn]

Is the "object" for the second lens not a "virtual object"? And, should the "Object distance" in that case not be negative?

[surendersingal]

In this exercise what gain we got in this composition lens where magnification is reduced to, 2 times?

[tylerlitch]

What screen recording software do you use? I would like to know a good one that allows me to pause recording.

[PaulineJacobs-yt]

It was nice but 3:14 the di had to be negative