GCSE Physics - Refraction of waves #63

In this video we cover the following:
- What 'refraction' means
- When refraction occurs
- How to draw ray diagrams for the refraction of light
- The idea that during refraction, the wavelength of a wave stays constant, and it is the wave speed that changes
Exam board specific info:
AQA - Relevant to all courses!
IGCSE Edexcel - Relevant to all courses!
Edexcel - Separate science only. Both foundation and higher tier
OCR 21st Century - Complicated mix
OCR Gateway - Separate science only. Both foundation and higher tierr
GCSE Chemistry playlist:
• GCSE Chemistry - Atoms...
GCSE Biology Playlist:
• Video
GCSE Physics Playlist:
• Video

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The one common thing between my brain and that light beam is that the knowledge going through my brain is just like that light beam going through a piece of glass. No matter what angle the knowledge hit my brain, it will still refract and change medium by going through my brain and out to the air. But, at least now I can use fancy words like refract and medium thx 2 u Cognito

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[@Cognitoedu]

If you’d like to practise what's covered in this video, check out the lesson on the Cognito platform - cognitoedu.org/coursesubtopic/p2-gcse-aqa-h-t_4.04. The platform’s totally free, and has been built to make learning and revision as easy as possible. The main features are: - Lessons organised by topic, only the lessons relevant to your specific exam board and tier are shown. - Automatic progress tracking. Progress bars tell you what you’re doing well at, and what you need to spend some time on. - Practise quizzes so you can test your knowledge. You can quiz yourself on any combination of topics you like. - A huge number of fully-hinted questions that take you step-by-step through some of the trickiest calculations & concepts. - A comprehensive bank of past exam papers, organised both by year, and also by topic. Amadeus & Tom

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[@yarofennedorp6817]

Could you maybe also create a video explaining how to calculate the refracted angle? because for my school that is needed, I don't understand how to calculate the angle because the teacher doesn't explain well especially during online classes

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[@envsh03]

There is no change of media, yet waves in a Ripple Tank are refracted (at a boundary between deep /shallow water). How can this be explained?

[@user-kf9oi9yw9u]

Excellent videos, but on this one the dispersion diagram towards the end is incorrect as the emergent rays refract back towards the normal rather than away. An important detail, as at IGCSE the examiners look for students to sketch and/or describe this pattern of refraction.

[@Abhi-wx9qc]

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[@michaelleask6548]

At 4:53, the spectrum exits the triangular prism incorrectly. It should refract downwards, further way from the normal.

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[@SimulatingPhysics]

For the ones curious, I leave here a explanation of why refraction happens: (It can be explained as a consequence of conservation of momentum of photons) If in medium 1 the index of refraction is n1 and in medium 2 the index of refraction is n2 and for the definition of index of refractions and wavelength we have: n1 = c / v1 , v1 = λ1 * f n2 = c / v2 , v2 = λ2 * f Dividing the above equations we obtain: n2 / n1 = λ1 /λ2 So if n2 is higher than n1, the wavelength in medium 2 is smaller than in medium 1. Now because the photon momentum is: p = h / λ Applying the conservation of momentum of the incident and transmitted photon along the parallel line of medium separation: p1 = p2 → h/λ1 *sin(θ1) = h/λ2 *sin(θ2) → n1 *sin(θ1) = n2 *sin(θ2) This is the Snell Law!! So the refraction is just a consequence of the conservation of momentum of photons!

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[@motivateyourself8506]

if speed increases, wave length decreases right?

[@affif330]

why does frequency never change yet wavelength changes if both are inversely proportional

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Hi, great vieos, helijng me understand a lot. Have any videos on snells law?

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thanks Aimen glad you enjoyed it

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[@davidmin743]

Hello, if the incident ray of white light entering a prism is combined (white), and the colours split apart by refraction causing various angles due to wavespeed within the prism, how come the emergent ray is not converted back into white light when entering back into the air? As the density is as it was originally. Thanks.

[@groggers]

You see, what you describe would be happening inside a glass cuboid, for example. When both boundaries are parallel, one would split the wavelengths, and the second would merge the wavelengths - again giving white light. Remember this: the normals in a cuboid are parallel. Since in a triangular prism the boundaries are not parallel, the normals are not parallel. When first entering the glass, the rays are refracted and thrown apart within the glass prism. On the second side of the prism, the angle of the normal changes. The normal is perpendicular to the boundary. When moving from a dense to a less dense medium, the wave speed increases and the ray bends away from the normal. Because of the different wavelengths, on the second side the split rays are bent to different degrees a second time, further distancing them apart. This is best understood with a correct diagram. I appreciate my wording may be slightly rushed but I hope it helps you to understand!

[@alaa.hassanabdelmoneim]

@@groggers Wow

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[@alyox_]

Hi! Great video, i just have one question. If something bends towards the normal, does that mean that it has a lower wavelength?

[@TheVkky]

Yes the wavelength is shorter as for the wave to bend towards the normal it will be getting slower and frequency does not change

[@alyox_]

@@TheVkky ok thank you!!

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[@ameliawibowo1489]

Can someone explain to me 0:48 where it said "the higher the density, the slower the wave" I heard somewhere that the higher the density, the faster the wave travel since the particles would be more closely packed together, therefore it would be easier to reach by the wave

[@christianomejesmath-phyaca1250]

Good question. For sound waves, the denser the medium, the faster the speed of travel, but here, it's about light rays.

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[@wendymcrae2272]

There is a mistake in the video description, where it says that wavelength stays the same during refraction. The video itself has the correct physics though -- frequency is unchanged, wavelength changes proportionally to the speed.

[@gohshunyuan3433]

may i know why during refraction the frequency will remain unchanged🧐~?

[@hannahkadic]

wait but how come when the ray enters a more dense medium it supposedly refracts towards it when in the diagram it looks like it bended away from it?

[@Reem-go4gg]

in a more dense material, the light moves towards the normal, and the diagram does show this

[@siddhantthacker8502]

Done sucribing

[@wilhorabin7694]

So the Refracted ray's angle is always half angle of incidence?

[@virajmokashi9303]

no he said to halve it because that's probably a level stuff or even higher so he said just to halve it

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when it’s slower it goes towards the normal

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4:55

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[@JoshuaLokz]

3:51 incidence and emergent ray need to be parallel?

[@Cognitoedu]

Hiya - Yes exactly - if the 2 sides of the object are parallel (e.g. 2 sides of the rectangle), then the incident and emergent ray should be parallel.

[@JoshuaLokz]

Ok thanks

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[@spookyking2307]

00:06 Refraction of light waves causes change in direction. 00:51 Refraction causes waves to change speed and direction when passing through different mediums. 01:24 When light passes into a more dense medium, it bends towards the normal. 02:02 Understanding refraction of light rays in glass 02:38 Refraction occurs when waves slow down and bend towards the normal in a denser medium. 03:12 Refraction occurs as light waves bend when passing from one medium to another. 03:54 Wave speed changes during refraction 04:30 Different wavelengths of light are refracted by different amounts Crafted by Merlin AI.

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mr K class?