Geometric Optics: Crash Course Physics #38

[@crashcourse]

We made quiz questions to help you review the content in this episode! Find them on the free Crash Course App! Download it here for Apple Devices: apple.co/3d4eyZo Download it here for Android Devices: bit.ly/3TW06aP

[@PeachyPatchwork]

Two helpful hints: Watch with captions and at 0.75x speed. And pause often to think if needed.

[@cait_frb]

Thank you

[@owencoukell388]

1.5 speed with no captions: Badass mode

[@itswarhawk]

@@owencoukell388 Ur cool but I don't wanna fail my exam lol

[@ori5278]

@@owencoukell388 ok

[@ori5278]

That doesnt really help apart from the pause often part

[@theangmister]

WE NEED CRASH COURSE MATHS

[@ayadimishra]

Angelo Thavaratnarajah I second this!!

[@malhaar5880]

U goddamn right

[@niaschim]

3blue1brown in the mean time

[@thebge1237]

Try searching for the youtube channel y mx+c The guy teach malaysian math but i think it will still teach you something

[@thebge1237]

Btw he speak english

[@ThePositiveTarot]

I sometimes watch the videos twice... The first time I just listen and get what I can get, which usually is a broad idea of what the topic is about, then watch it again the second time while concentrating, pausing, contemplating and taking screenshots as necessary

[@sofiatovedal7663]

Why do everyone complain about the speed of her speech? All crash-course videos are like this, it's the whole point to squeeze a bunch of information into a short video.

[@ameerhamza4816]

But it's not possible. People who don't know can't get this so fast

[@justfr4nk468]

exactly, at least it's not boring as a 3-hour class, and it's the same data but faster and more simplified

[@symbolofpeace.3846]

Oh come on friends... You can slow down the video by yourself ... I also felt that it's too fast, but there's way to solve the issue.... They are really doing a good work.

[@aksharaa5376]

@@symbolofpeace.3846 i definitely agree with you. it's best to fix the problem by fixing ourselves, rather than blame others. crashcourse does really put in a lot of effort, and we should appreciate it, rather than complaining

[@kiasmorningstar]

I personally struggle with holding thoughts more than 15 to 20 seconds at a time. The quick pace of this series is just right to hold my attention, and I feel the amount of information is just right. I have sat through these traditional courses, and after waiting for people who don't understand to ask all their questions I am already thinking of something else other than the subject matter. Thank you crash course.

[@brittniep9219]

If you struggle with following along at her natural speed (to make an information packed short video), I recommend choosing the 75% speed option. It is still relatively quick but much easier to follow along with for those of us that aren't as fast of auditory learners! :)

[@sarahzhao9347]

She was wrong that the image is always upside down for converging/convex lenses. If the object is closer than the focal point, you will end up with a vitual image that is upright.

[@_gammingsultan7162]

🖒

[@hiyashah2335]

Periodt

[@Chris-vx9qp]

I learned and easily consumed more knowledge from this 10 minute video than I did in a week's worth of intense focus towards this exact subject in science class.

[@avinashbinand9272]

I'm so glad this channel exists. It's the only thing apart from my dad keeping me from failing physics.

[@shawnsea624]

Thanks!

[@darknightofthesoul8980]

If only more ants had umbrellas.

[@fossilfighters101]

+

[@AlexandreG]

Dark Night of the Soul now I understand I was an evil kid

[@tiaradsouza2072]

Dark Night of the Soul I.

[@dapet2258]

I did that with other bugs. I wish other bugs had umbrellas too.

[@millie9858]

When you got a science test next and didn’t understand anything in class

[@jebus6kryst]

The Star Wars reference was awesome.

[@fossilfighters101]

+

[@conormahon845]

Thank you for giving the ant an umbrella

[@edwardbackman744]

Why do I even watch these I can only follow them for the first 3 minutes

[@chingalingaling]

Pause button. Notebook.

[@kurtpace1545]

I know cause they are thrash

[@ThePositiveTarot]

Slow down and/or repeat

[@aster4405]

@@kurtpace1545 no u

[@shanthala1345]

@@kurtpace1545 they'r not!😭iam surviving high school! thanks to crash course.

[@user-yc7ub3dj5t]

This video has taught me more than the hours worth of lectures I attended for this part of Physics lol, channel never fails

[@flamedragon07]

I agree. I love the Rogue One and the Last Jedi Prophecy references. Keep up the wonderful work. Yes, I wish they had Crash Course Math also. I could use the math help.

[@adventure9119]

I love the Rogue One reference :D

[@Emily-on9jq]

You know you've watched too much CrashCourse when you recognize that the animation is Scout Finch.

[@jahsoka8307]

1:16 Last Jedi prophecy!!! They knew🤔

[@yeknomican]

The whole point of "Crash Course" is that it is presented in a "crash" of information. The whole reason why it works is as a supplement to proper lectures, or with liberal use of either the pause button, or the replay button. This has been true since the beginning of this channel. - verdatum

[@andomadsen3743]

Turning a blurry world into a high-definition experience... yep, very much an accurate summary of my experience each time I update my spectacle prescription.

[@bridger1221]

This video alone got me through grade 10 optics! Thank you so much crash course!

[@fawazsm]

5:23 focal length of lens depends on refractive index also ... the relation given there is that of a mirror.

[@dianaanonymous5794]

THANK YOU THIS HAS HELPED ME IMMENSELY

[@Zikiss]

0:21 Love the Mirror Master appearance.

[@frhneil1463]

Great video! I have a physics exam tomorrow and i just not into reading tonight, and thought that this video explain almost everything from my text book! Greater ways to study, P/s : read that some people thought that the teacher is talking too fast. I think that's not a problem though, some people need to study in a fast way, so they need to make a video no longer than 10 minutes. For those who can't catch up what she is saying (which happens to me too) I recommend you guys to pause the video to digest all of the information in your mind before moving on to another new information. Have a great day ! ♡ And the animation is so cute!

[@whatthefunction9140]

OMG I thought that robot was wacking it for a sec. 0:56

[@MisterBrrown]

lol

[@idontgiveafuckaboutanythin4310]

Dylan T u have a dirty mind

[@suhanahussain7]

@Idon'tgiveafuckaboutanythingH Lol u have it too...xD

[@H3yItsAmanda]

SAME

[@Danilego]

it’s K2SO!

[@yousefabdelgaber7498]

This was the first crash course physics video I could keep up with first go

[@eatingtacos000]

Hate to be that guy, but you really have a special ability to explain a relatively simple concept in the most confusing way possible. If your audience includes people who do not know what refraction is, then speeding through the sentence "this phenomenon of light rays changing direction at the interface between media" is going to leave them clueless. I know the point of this channel is to teach quickly, hence "crash course", but you aren't teaching at all when you talk like that. Just some advice from a teacher. Peace.

[@verdatum]

FWIW, it's REALLY hard to write something that's compact and makes perfect sense to all audiences on the first viewing. And this is especially true in the realm of physics. I think that's part of why the viewcounts on CC Physics tend to be particularly low. I often try to think of how I could write a better episode on the topics, and yeah, it ain't easy.

[@ajaxhopper9859]

Following Feynman Of course, this is meant to _supplement_ a physics class, not necessarily replace it.

[@torestgard1681]

Legend Length: the problem is that before your brain has processed the information in this sentence, the presenter is far into the next sentence. The natural pause between the sentences, whatever originally was there, has been edited out to speed it up even further. It is speeding through complex sentences which is the problem, not the complex sentence in itself.

[@mirandachen4846]

Following Feynman c

[@ayadimishra]

Following Feynman I agree, this has made it less enjoyable , she just seems to be speaking , not teaching...I needed help with my exams , but that didn't work out well I guess 😖

[@Dribbles88]

Love it!!! We cover this in Physics 223 but in great detail. Great review!! THANKS!! Keep them coming please!

[@pasteltwighlights9437]

i had to watch this on my online class 😭

[@heimskr2881]

Im doing that now :)

[@ayadimishra]

CRASH COURse MATH PLEASE 😢😢 now that we have CS , MATH NEXT!!😣 ...btw, thank you for CS 😊

[@TheFireflyGrave]

I've never tried noticed that straw illusion, one day I'll have to give it a try... maybe right now.

[@matthewhall319]

CrashCourse should do a Crash Course to how you make Crash Course.

[@zachydrogeo]

now I'm wondering if optometrists know as much physics as engineers...

[@veronicas8270]

I was thinking the same thing! They must know something about all of the lenses they switch in front of my eye. Probably not as much as engineers, but they must know stuff about light and lenses.

[@brittniep9219]

Optometrists do have to take physics! They then specialize differently than engineers.

[@olohijeozolua8366]

I love listening to you 😍😍😍 so much to learn 😍😍😍

[@clintgolub1751]

This was exactly what I was looking for!

[@hayakiliyanni9920]

she has a good pronounce in English and we have to slow the speed to understand it actually the correct pronounciation make it difficult for me but still i can understand the way of teaching. and i can understand everything about light in this video

[@joshuamitchell5530]

7:03, not exactly true as a convex lens can produce a virtual image which is upright.

[@hidude1354]

In terms of Real Images, she is correct.

[@andrianinikolaou6618]

Great video! Such videos are extremely important to me, as my school teacher is useless 😂 We this I finally got to understand reflection. Very helpful! 😊❤

[@Vipin-kq5mg]

Thank you so much... You saved my life... Wonder Woman 😍😍😍😍

[@sfruizmiranda]

I LOVED THE MIRROR MASTER REFERENCE!

[@ahmedabdalla8849]

At 7:02 you stated that convex lenses always create upside down images. But don't they create erect ones if the object is with a focal length of the lens?

[@StillMintTea]

That unfinished 5x5 always distracts me ( the cube, ppl)

[@howareyou9158]

I have been waiting for this topic for one year!

[@ArianaCabello]

They just had to use the rogue one reference which made my night 😂😂😂

[@AyeshaKhan-gp9on]

I'm soooooooooo glad that Shini went slow this time. In the videos on electricity, magnetism, electromagnetism and Maxwell's equations, all she did was show equations at a breakneck speed.

[@geethanjalinagiri9714]

What my teacher couldn’t do in ten weeks, crash course did in less than ten minutes

[@ANITBIOTICS]

crash course: the only thing that is stopping me from failing my class homework

[@Hamraali]

great explanation!

[@josiahmongru8197]

cc is a life saver

[@160p2GHz]

Wish I'd had this resource when I was first learning this :*D

[@sunnysingh-lh8nw]

She is a wonderful teacher that makes the topic very clear.... She is flawless..... Love crash course physics because of her. Thanks

[@miguelsobrevilla7673]

Appreciate, I have an astigmatism. Thanks. The angle is the result of crying, then a promise. Side rear mirrors are based on this theorem.

[@shamnamuneer6597]

Crash course is my favourite channel 😍😍😍😍

[@zainababdullah6690]

Thanks so much 💙

[@FireBucket]

Will you guys do an episode about shadows and darkness ?

[@TheLowstef]

The info box at about 5:30 is wrong. The focal length is half the radius for mirrors, not lenses. The lens formula is more complicated

[@smotmot]

Is there a mistake at 3:15? Says the higher the index of refraction the smaller the angle, shows the opposite.

[@valerianmp]

A good thing to start a day

[@TheSammycorreia]

You guys should do a series on marketing ... Great vids

[@arielthomas8737]

0:47 is looking more likely every day

[@gabrielserafin5215]

The infinite Rey pun has so much more meaning now !

[@FishTankEnjoyer]

You did very good!

[@Robotcazplays]

Exam in two days, this is on it and this really helps Thanks.

[@SeemaYadav-ok2us]

Anyone here during stay home stay safe campaign pandemic with zoom classes, press like

[@geoffreypagcaliwagan3024]

had a test about this last monday. wouldve been really helpful :(

[@mentalaids3220]

aw

[@convergentseries3508]

exams lul

[@TGC40401]

I like this show. Keep it coming lol... Although I've already done lots of this stuff lol

[@volume8831]

What’s good is that you can go back and listen again if you get distracted compared to skl Lol.

[@ollieoreoo]

Bombed my first optics test so I'm here XD thank u

[@ninjaxish]

Got a bit confused @3:06. She says "the higher the index of refraction, the smaller the angle", but the image shows the "Low Refraction" side having a smaller angle of refraction than the "High Refraction" half. Can anyone clear this up for me?

[@ameerhamza4816]

I think they measure angle from horizontal line instead of vertical

[@shashwatsingh9698]

umm....isnt the magnification for lenses v/u instead of -v/u in general... also i think the sign in the lens formula is wrong.

[@shyambhadra2009]

Do you have any videos about convex and concave mirrors?

[@sfruizmiranda]

I loved the Mirror Master reference

[@ekim5589]

Question: for the last two sentences, she said that if the "image is upside down like in our converging lens, then the height is a negative value. And the ratio of the image distance to the object distance is also negative" If the equation is m [magnification] = hi/ho= -di/do, then how can this be true? If the image height is negative, shouldn't the image distance to object distance be positive to maintain the original equation?

[@hidude1354]

You are correct that magnification can be shown from height and distance, but your formulas are incorrect. For height, it is: -(Object Height/Image Height). And for distance: -(Object Distance/Image Distance). Therefore, both equations are equivalent.

[@thomaskoning3985]

This video taught me more than my physics professor in a month

[@torestgard1681]

Woh, woh, woh! SLOW DOWN! In normal crashcourse videos it is good to edit out the pauses in speech to get a quicker and more fluid video. In physics it does not work. The audience need the time to reflect on what is said, to grasp it, but the time is never given. Instead she just rushes through the script at neck breaking speed. And to top it off, throw in the occasional formula without explaining the symbols and hurriedly take it away before continuing rushing on. This could've been a great and instructive video, but sadly it isn't, because of the editing. Stop taking away all the pauses between sentences!

[@DeadPyro96]

There is a pause button.

[@benedeknagy1]

Tore Østgård yapp... And a repeat button in the end

[@torestgard1681]

Indeed there are. And they were deployed. You can only pause and rewind for so many times till you get fed up. This was sadly the last episode I saw in this series. The topic is very interesting, but I cannot recommend this series. I recommend any other Crashcourse series, even literature, which is some mean feat as in school I hated literature, but loved science.

[@DeadPyro96]

I am currently studying Astrophysics at Uni, so I don't think it's that fast, but that's because I already know pretty much all of this. I suppose a person who doesn't will find it too fast. The ones I recommend the most are History and especially Astronomy. Phil Plait is such a great presenter and the whole series is wonderful.

[@torestgard1681]

If it takes a student in Astrophysics to follow it, it is clearly to fast-paced :) Target audience is high school students, isn't it? I'm a Uni student in physics as well, or rather chemistry perhaps - a mix of both really, so I think I have OK background. Still I feel the need for additional 0.3 seconds between sentences so that I have the time to verify what she says is correct. Both series on history are great. "wait for it... the mongols!" recurring joke! :) I liked the astronomy-series too. Great presenter! Most presenters are good, including this one, but the edit people let her down. I actually hoped the astronomy would be more advanced than it turned out to be. Thus I had great hopes for Physics.

[@MrJayPuff]

Awesome job!

[@hibiscusman]

Guys. De-Esser on the narration. Pleeeease. Everything about this show is so beautiful and perfect, except the audio. It burrrns ussss...

[@jamaluddin9158]

hang on, doesn't convex lens form a virtual image when the object is placed between focus and pole?

[@Jana-cw8xf]

really helped me understand! thanks x

[@bottomtext593]

This is my least favourite physics topic simply because of how hard it is to visualize

[@sookiesister312]

This is very helpful thank you

[@iancostello3923]

Who is the designer who does these animations and does he/she get technical assistance on them?

[@erick.gudino]

great! all your videos are so clear and useful!

[@nat29_]

want a lesson for separation of compound in mixtures and composition of a mixture

[@orianmenashe8661]

You guys are amazing this video helped me alot with my physics exam!!!

[@jetungnnifer]

Please do computer science!!!! PLEASE

[@shiromiemotionless2955]

Jennifer Tung done!

[@blazegaming8267]

They have itt

[@fahd2644]

very yes

[@spanishlatte9422]

Isn't it a concave mirror is the converging lens while the convex the diverging? I'm confused.

[@tapansapre8578]

Really informative video!!!!!!!!!!!!!

[@satyamsingh9695]

You Saved my Literally

[@lilit3552]

Thank you so much, this really helps me.

[@jerrysun44]

Watching the video when you have a Unit test tomorrow. Lmao

[@Ukid111]

This is torture. When you already know this.

[@ThePhoenixpaw]

So, how do you calculate "Dioptre"?

[@null090909]

I find it sad that crash course would not spend 1second explaining WHY light bends in the first place (because it always follows the fastest path). I find this fact fascinating.

[@science-y9209]

Do tell me if i have my fact wrong but it's 1/v-1/u=1/f in my book and getting confused now cuz even when i googled it ..but most of them consented with mine but some of them had that formula too ...😐

[@Shreyasiiiii]

This formula is correct... But,, it's called lens formula..n it's applicable to spherical lenses... N mirror formula is: 1/v + 1/u = 1/f

[@FroehligGirlz]

So, I'm near-sighted, and effectively only see a virtual world... at least more than 6 inches from my face. How bizarre.