all right continue from our last lecture um we were discussing at the end of class uh electromagnetic spectrum okay electromagnetic specs spectrum is the collection of all electromagnetic radiations okay based on the order of their energy frequency and wavelengths okay and on the spectrum that we're drawing here from left side to right side you can see our energy of the of the radiation is increasing okay since energy equal to planck constant times frequency that means frequency is also increasing okay and things since frequency and wavelengths are inversely proportional to each other so that this also means from left side to right right side your wavelengths would be decreasing so gamma ray would have the lowest wavelengths okay in the different radiations that we listed here on the spectrum and it would have the highest frequency and the highest energy and we discussed everything on the right side of the visible region already starting from in the middle it's invisible and then ultraviolet x-ray and gamma ray and these guys are on the high energy high frequency low wavelengths of visible region beyond the violet end of the visible region okay and as you know from the rainbow color okay rainbow is actually the visible light spectrum okay so one side of it is red end and the other side of it of the rainbow is the violet end okay and beyond the red end would be the lower energy lower frequency and longer wavelengths radiations okay right next to the visible region is what we call we use ir to represent it this is infrared radiation okay and this is what people um i think the most kind of real-life use of it okay you've all seen night vision goggles okay night vision goggles tracks um and heat of objects and now that heat wave is actually not exactly heat but the radiation caused by heat and that's the infrared radiation okay uh the night vision goggle has sensors um catch that and through technology kind of translated it into um visible light okay so what you're seeing there okay is not visible on this through the night vision goggles okay is not visible light okay that's why when you look in that direction it's with your naked eyes it's completely dark okay but the infrared radiation was catched uh was caught by the sensors in the night vision goggle and then that signal okay on the sensor was translated into visible light the green image or red image that you see okay through the night vision goggles that's infrared radiation okay and then even lower energy compared to the infrared is microwave okay microwave isn't that what we use in the microwave oven yes it is okay the micro the microwave oven use microwave one form of electromagnetic radiation okay to heat up food all right so then you go this is supposed to be lower energy because this is on the left side of the visible region are you saying that microwave should have lower energy compared to visible light individual photon wise yes that's true okay but i didn't see people using visible light to heat up food well you could okay putting food under direct sunshine in summer does cook it does raise temperature raises temperature okay but if your microwave photon have even lower energy why do we choose that to heat up food if it doesn't provide a lot of energy well let's clear something up here and we actually touched based on this on the other day when we were talking about photon energy a individual microwave photon will have lower energy than the individual visible light photon okay but when we are utilizing these all of these different radiations nobody is using just one or a few photons okay instead now the machine inside your microwave oven okay is creating literally billions of billions of billions of microwave photons okay in a very short frame of time and yes one individual photon it's low energy but even one individual photon of gamma ray would be very low energy anyway plane constant is the smallest constant you've seen in this class 10 to the negative 30 force okay it's when you have a ton of those photons now then energy accumulates so if you can send a ton of microwave photon into your food okay through 30 seconds as long as long as you put enough number on the on the photon okay then your food is going to be heated up okay doesn't matter if your individual photon doesn't pack too much energy all right so that's microwave and then below that is radio wave okay when we were talking about fm am radios earlier okay they fall into the radio wave region okay and when we were talking about wi-fi signals or cell phone cellular signals they fall into the radio wave region as well okay and much longer wavelengths much lower frequency and lower energy for photons all right so you don't have to memorize numbers you know energy or frequency or wavelengths of these different electromagnetic radiations okay but you for for our classes purpose okay you need to know okay generally which one of these radiations have higher energy lower energy higher frequency lower frequency higher wavelengths lower wavelengths okay you you kind of need you need to know the order of it okay no numbers required all right so as we are discussing the energy part we touched on this concept of photon and a photon is an individual packet of energy for a specific um type of radiation now and now both of these so at this point we've talked about electromagnetic radiation at the beginning as a wave remember the wave that we draw the electric field the magnetic field the wavelengths all that stuff okay and then on the other's hand when we're talking about the energy we're also viewing electromagnetic spectrums as particles photons right sounds like neutrons electrons okay all those are uh basic particles protons all those are basic particles that exist and make up our word okay photon is a word created in that sense but it's pure energy it's not material it's no material it's pure energy okay but we view a photon as an individual pack okay individual component of a particular type of radiation and once people observed both end of the property now i'm not talking about spectrum here we're talking about the electromagnetic radiation is a wave and then when we discuss the energy of it we also view it as a particle what kind of sun can be a wave and a particle at the same time that sounds weird and unimaginable okay can you picture something that's a particle and a wave at the same time and but on the other hand both properties okay the individual particle property of photons okay energy of electromagnetic radiation comes in you know individual packets that is scientifically proved okay people have different kind of experiments have long proved that electromagnetic radiation lights do that their energy do come in packets okay and then the wave property of electromagnetic radiation is also long proved and utilized okay how do you think we do radio okay we created radio wave that has frequency has amplitude all these different wave properties that can be adjusted and to carry radio signals and today to carry your wi-fi signals carry all kinds of data right yeah so the wave property is also long proved so everything that we know at this point okay is telling us that electromagnetic radiation and lights are both waves and particles and this special property okay of electromagnetic radiation is called the wave particle duality okay again this is not an easy concept to digest okay because it's just so abstract it's so unimaginable you just can't picture something that's a particle and a wave at the same time but yet it's proved for the radiation and ever since people proved that electromagnetic radiations light lights are is having this wave particle duality people have then start to consider is electromagnetic radiation the only thing that have that has the wave particle duality are there other things that can act as can have the wave particle duality or like to extend things a little bit okay now electromagnetic radiation or pure energy with no material okay so it's mainly a wave because we use its wave function way more than we use the particle function it's a wave okay but it has particle property when it comes to its energy okay are there things that's kind of materialized okay that are particles that actually show wave property if a wave can show particle property can a particle show wave property and of course now for a long time that doesn't make any sense to people okay what do you mean particles have wave property a flying bullet can be viewed as a particle right i've never seen even with the best camera okay i guarantee you you won't see a flying bullet okay go wave around and a baseball throne okay can be viewed as a particle flying do you see it going up and down left and right four wave no and if you're viewing from you know three thousand feet above okay moving cars on the ground looks like particles okay but do you expect to see the car looks like a wave well unless the driver is drunk you probably won't see that and even if the if it is okay the way we're talking about here is something that's having strict wavelengths frequency and a drunk driver wouldn't be able to do that anyway so for a very long time people's answer to that question is wave can have particle property okay when it's pure energy and no material but when you have material when you when the things are viewed as a particle like a bullet a moving car a flying baseball or even an atom or a proton electron okay when they're particles no they shouldn't have wave property because we can't see it okay now that sauce eventually went away okay eventually people start to recognize that all particles all moving particles okay even if they have mass even if they have material even if they're not pure energy would actually have wave property as well all particles actually have wave property so what does that mean that means wave particle duality is not something exclusively reserved for electromagnetic radiation okay wave particle property now the weight wave particle duality now is viewed as a widely existing okay scientific scientific effect for all particles whether you have material or not okay and beyond that okay people even now know okay the relationship for any given particles okay people know how to figure out the wave property of them okay and that relationship between the wave property and the particle property is called the broccoli relationship okay so this is the relationship between particle and wave nature of all moving particles okay and this relationship can be represented with a very simple mathematical equation and that is wavelengths of a given moving particle okay should equal to h the plane constant over mass of the particle times velocity of the particle so this is the planck's constant this is the mass of the particle this is the velocity or speed of particle okay and now if you remember okay plane constant have unit jurors times second and mass international standard unit is kilograms and velocity international standard unit is meters per second okay yeah and this unit here okay is eventually meters and if you're wondering why well jour essentially is kilogram meters square second square times second divided by kilogram kilogram cancels divide by multiply by meter per second so that second flips up and all four seconds cancel and meter cancel one of it you end it up with meter okay now anyway so we have this relationship and of course you look at this you go how do you know okay are you saying that every moving particle with mass okay actually have some kind of wavelength yes that's exactly what i'm saying here okay but why couldn't i see it well let's do a couple examples and also if i don't i can't see it then how do you know it exists so let's see that from a couple of examples here okay so first example calculate the broccoli wavelengths of a one pound ball flying at 97 miles per hour so let's say you're throwing this fastball okay and we're trying to calculate okay this was flying fastball as a big particle okay it has mass it has a velocity what kind of wavelengths it has okay all right so of course we need to use international standard unit one pound okay so one pound equals two point four five three six kilograms okay 97 miles per hour if we can do some calculation you can directly turn this into about 43.36 meters per second all right so your wavelengths should equal to a plane constant 6.626 times 10 to the negative 34 over 0.4536 okay kilograms times 43.36 meters per second and the result of that is three point three six nine times ten to the negative thirty fifths okay now this is not a conversion problem so i'm not really worrying about the conversion and that's why i gave you the numbers directly okay but the calculation is showing you why even with the best camera in the word okay you won't be able to see the wave property of a flying fastball because the wavelength is so small that right now with all the technology that we have we can measure a length this small what do you mean well let's put it this way a atom okay is probably the limit of the smallest size that we can observe at this point with our technology and size of atom is actually in the 10 to the negative tenths meter range okay now and what about 10 to the negative 35th meter okay you need to blow up the size of a atom okay to the size of our current known universe okay and this wavelength is still something the size of smaller than atom after all that zoom in after all that expansion okay this is still a size that's hard to measure okay not even in the same area code when it comes to measurements okay this is about as low as we can do now there's no way you can measure that there's no way you can measure that in my lifetime and possibly most likely in your lifetime as well okay so you're saying that every moving object has a wavelength okay and you created this equation for us and after calculation you're telling me those wavelengths are so small that i'm never going to be able to measure it that doesn't sound scientific does it that sounds a little like snake oil salesman you created this song this equation and you name it after someone okay this french name and or whatever european name but you're telling me that what you calculated i would never be able to prove it can i does that mean i can create something and use my name on it and say it's a scientific law relationship or whatever no okay this is an example simply telling you why we can't prove the wave property on a massive object something that we can see okay but of course there need to be something that you could see and you could measure for for you to be able to say well this is actually how it is the next example here is something that people ended up saying but we could see this all right the next example here is something that we can actually prove and measure calculate the wavelengths of the electron in hydrogen atom knowing that the mass of the electron is 9.11 times 10 to the negative 31st kilogram and the velocity is two point one eight times ten to the sixth meter second okay now and the calculation itself again is not something that we focus on because it's just plug and chuck six point six two six times ten to the negative four thirty 34th over 9.11 times 10 to the negative 31st times 2.18 times 10 to the sixth okay and this calculation gave you three point three four times ten to the negative tenths meter okay so we know this and we measured this okay the mass of a single electron is 9.11 times 10 to the negative 34 31st kilograms and the speed of that electron the average speed of that electron is about 2.18 times 10 to the 6 meters per second so it's an extremely small mass moving at a very high speed okay and this is how electrons move about inside that hydrogen atom that only have one electron okay so put those two numbers into your uh the broccoli relationship calculation you found oh okay the wavelength of that electron okay is actually three point something times ten to the negative tenth meter all right so you go it's still a very small number it's still a very small wave property what good does this do well here's the difference between this and the previous wavelengths of the fastball okay that is a number that we can't measure okay and we probably won't be measured able to measure for a long long time this remember we said the detection limit nowadays or the smallest distance that people have is around 10 to the 10 negative 10 meter this is some distance or wavelengths that actually fall fall into our measurable range okay yeah and to just show you how significant this wave property is okay size of a hydrogen atom okay is actually about so the diameter of a regular hydrogen atom is about 2.4 times 10 to the negative tenths meter see something here the wavelengths of the electron is actually bigger than the size of the space is flying in okay yeah and back when we were talking about atomic theory okay we talked about how uh the size of the atom compared to the size of a nucleus okay we say generally speaking compared to the size of the atom the nucleus size is about a football to the entire football stadium that's how much empty space that you have in an atom using that rationale okay the size of the electron compared to the space inside atoms is probably close to the comparison of a small bullet and a big football stadium okay so imagine this one bullet okay tiny metal ball of a bullet is flying in a huge space the size of a stadium okay and now that is your stadium for the hydrogen atom okay so now imagine this small bullet is that's flying in there actually have a wavelength of bigger than the football stadium it's flying in okay you know for sure your electron in that sense is not flying in straight lines it's not flying in circles okay yeah and but hey we can observe electrons at this point with our technology we can very care accurately measure the properties of electrons this is something that we can actually prove that works okay the wave property on the electron absolutely exists and can be observed okay and that's why we have the broccoli relationship standing nowadays okay for bigger project for large massive particles the wave property can be observed okay but for extremely small particles wave property do exist and can be observed okay and that's why today we believe in wave particle duality okay if it happens on the small particles okay we believe it should also exist on larger particles because there's no reason why it wouldn't we can't observe it on large particles but we could observe it on extremely small particles like a electron okay now whether it exists on large particles right now we essentially assume that it does exist on the large particles until you find proof okay to say no you're wrong it doesn't exist here's my proof okay until then okay the scientific attitude okay is that it does exist they have no reason not to exist all right so that's what the wave particle duality is and we're not going to go too much further on this particular concept okay now for you for this chem 115 purpose well just make sure that you can do this calculation and remember take care of your units we're doing this calculation we're using kilograms we're using meters per second if you have any other units on your sorry exam for the broccoli wavelengths calculation turn them into kilograms turn them into meters per second and the next thing the next concept we're going to introduce um well um is about continuous spectrum and the line spectrum and then that's what is going to lead us to the view inside of a atom okay and because of that reason i don't it's a long topic and i don't want to break it down and also i think i owe you guys a few minutes from previously classes that's going beyond 50 minutes so for today's class we're just gonna end it right here