Hello! This is a revision podcast for Excel I G C S E and this is on topic

3 waves. There are two kinds of waves: transverse and longitudinal waves. Longitudinal waves vibrate back and forth in the direction in which

the wave travels this could be a slinky spring here are areas where the spring has been

compressed. The spring will pass on that vibration to the adjacent particle. That particle will move forwards and

then move back into position. The wave moves across to the right but

the particles themselves move forwards and backwards. Areas where the waves are close together are compressions. And areas where they are spread apart are called rarefactions. Transverse

waves vibrate up and down across the direction

of travel in this example the wave is moving to

the right but the water (if it was a

water wave) or the particles would move up and then back down again.

The wavelength is the distance from one peak to the next and the amplitude from the

center of a wave to the top. Both of these kinds of wave

transfer energy although neither of them transfer any matter. The time period is the time it takes to make one

complete oscillation so that will be measured in seconds

which are the standard units for time. the frequency is the number of vibrations made in a second and that has standard units hertz (Hz) which means the number per second. In this graph you can see that as the time

period reduces the frequency increases. In fact the

relationship between frequency and time period is reciprocal frequency is one over the time period.

You are given this equation on the Excel paper. Here is an example using that equation: if a jigsaw blade vibrates up and down at a frequency of 80 hertz, how long

does it take to make one complete vibration? That’s the time period. You

rearrange this formula to make T the subject that will be T equals 1 over f. Substitute the data: 80 Hertz. 1 over 80 is 0.0125 seconds that’s the time period for the jigsaw

blade. The wave equation relates the wave speed to the wave’s

frequency and its wavelength. The letter lambda is a Greek L and that represents the

wave length as the frequency of a wave decreases the wavelength increases for example if the waves at the shore for beach arrive

at a frequency of 0.4 hertz and are eight meters apart, calculate the

wave speed. so you’d use this equation in this form wave speed would be the frequency times by the wavelength gives 3.2 meters

per second note the the units here are standard so

the output units are also standard units for speed – or

meters per second Any wave involving electromagnetic waves would travel at

the speed of light so if a question asked you: Radio one is

broadcasting a radio wave 97.9 megahertz what would be its wavelength? You’d rearrange this

equation to make a lambda the subject. So if you

use a triangle cover up this term and that leaves v divided by f. Lambda is speed over frequency so 3 x 10^8 over 97.9 x 10^6 that’s 97.9 million gives 3.06 meters When waves pass through a gap they

spread out slightly this process is called diffraction diffraction is greatest when the

wavelength of the wave that’s the distance from one peak to the

next is about the same size as the width of the gap and destroying the show’s about maximum

diffraction was the wavelength here is about the

same size as the gap when you draw these diagrams note that

the wavelength remains constant throughout distance here is about the

same as the distance here diffraction happens when there’s only

one edge in this case the gap is considered very

large and so the diffraction is greatest when the wavelength is very large I E a very long distance gap so a very

long way will def racked the most always to fract including lights but we

don’t observe like defecting very much because its wavelength is so small you’d need a very small gap to see its

diffraction you need to know about electromagnetic

waves which are oscillations electric and magnetic fields that may sound confusing but the part of

a family of well-known waves three from long wave radio waves to very

short wave gamma rays all electromagnetic waves carry energy but only the shortest wavelength ones

are ionizing gamma rays a very ionizing and

ultraviolet least ionizing all electromagnetic waves travel at the

same speed that’s the speed of light here’s a new moniker might help you

learn the spectrum in terms of frequency amp it starts with

gamma rays which are the lead shortest wavelength

and goes to radio waves which are the longest wavelength I can’t

claim credit for this demonic it was invented by one of my students generally the higher the frequency the

more dangerous the electromagnetic wave gamma X rays and ultraviolet are all

ionizing it’s not about some uses and some

dangers electromagnetic waves here some statements taken from the

syllabus ready way to use for broadcasting Mike Rice for cooking infrared for

heating visible light ultraviolet X-rays and gamma rays all have uses and hear

some dangers microwaves will he to internal body

tissue they don’t ionized a infrared can cause

skin burns it’s also not ionizing ultraviolet does damage to the skin surface cells

and blind and can cause blindness and gamma rays can cause cancer and can

mutate cells mirrors will reflect light according to

the law of reflection that is that the angle of

incidence is equal to the angle of reflection you measure angles to the normal line a

normal line is drawn at 90 degrees to the surface of the mirror you need to build to

construct a diagram to show the location of on image so here is an object that we’re looking

at and the image is formed the same

distance away inside the mirror so after all on the image location equally distant and

level with the object here if an observer looks at this object they will see the image inside the

mirror this ray diagram shows you how it forms

have the image forms here to start off with your ruler at the

position of the image and you draw or brave that goes to the

mirror and continues to the eye that ray would’ve come from the in the

object over here and it reflects at the mirror surface I’ve repeated that process for a second

ray of light and you can see that diverging spreading

out if you put your pencil at the object

position and join a lineup with where the ray

hits the mirror you will get an accurate reflection these rays reflect of the mirror go to

the RI these rays aren’t real they’re called

Virtual Race and they should be door drawn dotted now the diagrams complete we haven’t

image that’s inside the mirror the same

distance away but laterally inverted that is swapped

left to right and that’s virtual the image can’t be

formed on the screen from these rays nope really travel there

is no light here virtual raise to show where the

image appears you can see reflections mirrored surfaces and also obviously at

waters edge is refraction is what happens when a wave

changes speed here waves kept to a boundary and they

travel slower in this medium one side of the way

travels faster than the other side of the way and so it overtakes and they travel in a

different direction once they go into the other medium note that the wavelength is also shorter

in the slower medium this happens to light when it travels

into glass the angle of incidence is greater than

the angle of refraction as the light bends towards the normal a normal line here is at 90 degrees to

the surface as it was for a merit roaring an analogy to explain it would be a car

driving from tarmac into mud as the car drives towards the mud eventually one wheel gets to the mud

before the other we’ll this wheel will travel slower and this

will foster so the car will change direction one

side will be traveling faster and it will turn here the car is now change direction and once it’s entered the mud it will

continue going to straight-line when it leaves the mud on the other side

the opposite will happen and this we’ll we’ll get traction first

and the car will move back to its original path the mathematics of

refraction are that n the refracted index of the

material is equal to Sinai over synar and that

could be put into a triangle to help you manipulate the formula the

opposite of the sine function is signed to the -1 he normally press

SHIFT and then sign on your calculator you’ll need that in the examples so much

in light enters glass at an angle of 45 degrees

to the normal and refracts 29 of 30 degrees calculate

the refracted index formula here is used in this form Sinai over synar which comes out to be

1.41 that’s the refracted index at the glass

and it doesn’t have units it’s a ratio in this example we want to know what angle light will

refract T when it enters diamond at an angle diamonds refracted indexes

2.4 because we want to know what angle it

refracts to you we need to cap Hill 8 are of formula rearranges to give us sign a bar sign a

bar Sinai over N which comes out to be not point 319 that isn’t the angle of refraction bio to find that

we need to use the inverse sine function are is the inverse sin of the art so we

just got which gives 18.62 grease worth checking

when you’ve got an answer but a look sensible compared to the

original angle of incidence let’s consider what happens to light

when it tries to leave glass or more optically dense material

if it travels at a fairly shallow angle it will refract and leave the class it

bans away from the normal of course if you increase the angle of incidence

at the surface eventually the lights will graze along

the glass surface edge it does that at an angle called the

critical angle so acts the critical angle light bends as far as it possibly can along

the surface of the glass beyond to the critical angle litres got nowhere left to refract and

so it reflects inside to block all the light energy reflects none comes out

and so this is called total internal reflection the

relationship between two critical Anglesey and to refract if index have the glass

is this sign see equals 1 over N and you could

put that into a triangle to help you manipulate

it again to calculate the critical angle for perspex if you know it’s reflective indexes 1.4

again you start by calculating sign of the critical

angle which is 1 I’ve Iran with that number we then need to use the

inverse sine function again to calculate the critical angle which

comes out to be close to 45 or 46 degrees a prism can disperse light into its constituent colors here white

lights refracts when enters and refract again

as it leaves the prism but the refractive index of blue lights is slightly more the refracted index for

red light so it bends slightly more and the white

light is split into its constituent colors when light hits this prism its arrives

at the surface at the normal line and so it doesn’t

refract and hits this surface at an angle a 45

degrees to the normal which is above the

critical angle and so it reflects the same process

happens again here and we’ve used these prisons to create a

periscope SLR cameras use presumes to reflects

light down through the lens of a camera so

that you see a picture of what you’re about to take like can be transmitted along optic

fibers as a digital signal the light flashes on and off quickly to

represent am code of ones and zeros which is a binary code light hits the edge at an angle greater than

the critical angle between the two materials and so always totally internally

reflects analog signals take any shape or size

but digital signals are either on or of when you transmit signals along any in any medium noise

can distort them let’s have a look at the distorted

signals so he’s the signals with some noise

added to them you can see the analog signal has lost

some of its original integrity we could clear this up but it would be

less like the original shape whereas a digital signal you can still interpreters ones and zeros you still

know if the voltage is high or low or in this case if the

light intensity is bright or dim so digital signals are less prone to noise by interference

and the original can be cleared up sound waves along tattooed no vibrations

a family kills the air from a loudspeaker moves back

and forwards and Knox into the molecules of its

neighbors creating a compression wave like other way a sound can be reflected

at san ako it can be refracted and it can be

diffracted you need to know experiment to measure

the speed of sound to do so you need some people a large

distance away from a loud sound you use a gun you by the guy and you’d watch for the smoke the people

would start the stopwatch when they saw the smoke and stop it when they hear the bank they

do see question speed equals distance over time to calculate that speed but the sound to

take and travel there are other methods for working at

the speed of sound other methods may be more accurate than

this method but this method works if you connect a microphone to an

oscilloscope you can create a trace that represents the sound the trace would be voltage produced by

the microphone against time but the voltage represents

the position or movement of the microphone had the time period can be measured from the

time taken to from one wave to the next and you could use the

frequency former remember that was given on the pegs am

paper to calculate the frequency of the wave if you knew its time period higher

sounds have higher frequencies when object vibrates the Soundwave a

crate on this telescope will look different depending on the

sound is producing the app to cheat and the wavelength

represents the loudness on the pitch can you work

out which one of these waves his loudest and which one is highest the higher the pitch the shorter the

period over wave so this one represents the highest pitch

sound because it has the highest frequency and

therefore shortest time period the Bourne object vibrates

the greater the empty will be so be represents the quietest wave and the shape of a wave indicates what

was vibrating so love these were the same instrument

and the was slightly different instruments it

vibrates in a slightly different way humans here sounds from about 20 to

about 20,000 hurts although as you get older this high-end

tends to drop off

Thank youuuuuuu <3

Thank you so much, all your videos are helping a lot! 🙂

These videos are very helpful..I thank you utterly 🙂

06:00 whoever did that is a legend!!

Very helpful, thanks 🙂

This is so Helpful thanks

Thanks alot !! So helpful 🙂

This is really well done thanks!!!

16:51 PLEASE USE WARNINGS, THE GUN SPOOKED MY PANTS OFF

thamks alot

These videos are great 🙂 But what about things like the rules for total internal reflection and how optic fibres work along with their uses?

omg this is actually helpful thx!!

5:37 you say gamma has a high ionizing power, doesn't it have a high penetrating power and a low ionizing power? please correct me if im wrong

greate vdeo thanks alot

Great video!!!Well, don't we need to know the experiment to measure the speed of sound using resonance?

There is nothing on the specification about an experiment to measure the speed of sound using resonance. In fact, resonance is not mentioned either, so it's unlikely that this will be examined. But Edexcel have surprised us in the past!

Great Vid , Thanks alot 😀

That was really usefull exams tomorow great podcast

Thnx

excellent video. thanks. our exam is coming after 2 months. any tips on revision of physics theory

Thank you very much. Just to make sure, do this playlist plus the playlist consisting of the extra parts related to CIE IGCSE cover the entire CIE syllabus? Also it'd be great if you post any notes you pass out to your students. Thanks again!

This is very very useful thanks.

thanks a lot for this video but what about the experiment how to measure speed in air using a resonance tube 😅

Thank you for this podcast

An easy way to remember the order of the EM spectrum is

Richard Made Ingrid Vibrate Using X-rated Gadgets

I am deeply upset that my impeccable revision notes have been ruined, by what are in general useful videos. I am talking in particular about YOU drawing a straight virtual image line, and then a dotted line (8:01), causing me to ruin my needless to say, spectacular notes. EXTREMELY ANNOYING! For a man of your academic pride, I expected better, than this low grade apathetic approach.

best source for physics revision. Excellent video!

the mnemonic for EM spectrum waves by the edexcel igcse revision guide is

"R"un "M"iles "I"n "V"ery "U"npleasant e"X"treme "G"ames

thank you sooo much for these videos! umm i had a doubt,is edexel similar to CIE igcse?

and also why should there be a long distance when measuring the speed of sound (the gun experiment).

LOL UGLY VIRGINS XD

will the speed of light be given on the examination?

Thank you sir, very helpful for my exam tomorrow!

Great video and it really helps my revision, but haha that gun sound gave me a fright lol.

your videos are the best, really encourages me to do well and study physics………….

thank you !!

halo sir thank you for your well explained videos i am not really good in physics and I think your videos will help me 🙂

Mann you are awesome 🙌

Thank you sir. i have my mock exam next week and i hardly understood anything about waves in class these videos are so helpfull. p.s i hope you dont mind but i downloaded the video😊

Another great vid. Keep up the good work.

Thank you so much for these videos, got 96% on my test :

Thank you so much for this! Waves has been my worst topic for a while now in Physics but now I think I finally understand it.

that gun sound, holy

https://m.youtube.com/watch?v=bjOGNVH3D4Y

Sorry if this question is interrupting if the pitch is decide by the time period ,so what is the frequency of a sound wave determines its?thank you so much for those videos it is really really helpful!

Thank you so much man.you like the best physics teacher

You're currently saving my life, you're an absolute legend thank you so much.

Thank youu so muchh! it was veryy helpful 😀

However i freaked out when i heard the gun shot HAHA i wasnt expecting that at all

The mnemonic i learned is

Rugby match is very unlike xylophone game

Does this also apply to Cambridge igcse (0625)?

Giant Xylophones Usually Live In My Room

Transverse and longitudinal waves: 0:09

Time period and frequency: 1:21

Wave equation: 2:31

Diffraction: 4:01

Electromagnetic spectrum: 5:08

Mirrors: 6:58

Refraction: 9:12

Total internal reflection: 12:25

Prisms: 14:03

Digital signals: 15:03

Sound: 16:13

Oscilloscope sound traces: 17:54

the boards specification for igcse are changing this year,will u be posting videos on that as well??

6:00 hahahaah ok den :')

can u say zero instead of naught thanks

"I can't claim credit for this mnemonic, it was invented by one of my students"

well played ben, well played….

Quick question, is this all of waves in physics igcse edexdel?