hi this is Mrs Hallock and this is your podcast on light and the electromagnetic spectrum what is visible light visible light is the light that we can actually see that's why it's called visible if we think about how light travels and we detect it it comes in through our eyes in this direction and it gets processed at the back of the eye called the retina and the retina sends a signal through the optic nerve this is your optic nerve to the brain and we can actually detect it as color and here you can see the different colors over on this side if you notice the patterns of colors they look like waves well that's because light travels in waves let's talk about the different properties of visible light visible light is light that has a wavelength between 400 and 700 nanometers nanometers have you heard the prefix Nano before it's a very small measurement you may have heard of nanotechnology that's technology used in computer chips and things like that very small devices prefix is nano it's a metric prefix and one nanometer is one billionth of a meter it's very very small or we can think of it as one meter is 10 to the ninth nanometers okay that's a very large number it takes a lot of nanometers to make up one meter if you can picture in your mind picture a meter stick so 10 to the ninth a billion nanometers make up one meter stick you want to make sure you write that down if you notice you can see the different patterns of the Waves here see how this wave excuse me the violet color the waves for the Violet see how short they are as compared to up here at the red this 400 nanometers is actually the wavelength for Violet and the 700 nanometers this distance here is the distance for the red so we're going to be talking about the visible spectrum a little bit in class you're going to be using it in activity so we want to take note that Violet has a short wavelength and the red has a long wavelength different wavelengths make different colors so you can see the different wavelengths here make different colors notice the pattern of color red orange yellow green blue indigo violet this is reminiscent of the Roy G IV the colors of the rainbow invisible light has a wavelength that our eyes can't detect well we're going to look at the electromagnet magnetic Spectrum you can see that down here there's a lot of wavelengths of light that our eyes can't detect let's talk about some examples that you're familiar with I'm sure at some point your life you may have had an x-ray you can't see x-rays it's invisible light UV light you're exposed to that every day where are you exposed to that the Sun infrared light microwaves radio waves and this is where your cellular waves come from they're radio waves these are all invisible light we can't detect them we can't see them okay we can only see this small portion right here this is the visible spectrum this is called the Electro magnetic Spectrum this entire line that you see here this is the electromagnetic spectrum Spectrum you can see this reflects the frequencies and the wavelengths of these different energies so at this end we have gamma rays gamma rays have a short wavelength you can see a very short distance between the waves here the wavelength is the distance between the two peaks a high frequency high frequency means yeah there's a lot of waves here that equates to higher energy that's really important you want to highlight that put a star next to that higher energy higher frequency takes a lot of energy to make these waves right whereas we go to the other end where we have longer wavelengths a longer distance between the two peaks here and we'll talk about the parts of the wave on the next slide but big distance between the two peaks that's lower frequency low frequency which equates to lower energy you want to put a start of that so it doesn't take a lot of energy we're just kind of moseying along to make these waves that equates to lower energy look at the types that are lower energy radio if you think about it when you're listening to the radio does it harm you no it's a low energy frequency or a low energy wave when you come down to the other end so microwaves we're moving in this direction microwaves are they damaging no they really are not infrared no visible okay visible light we know is not damaging however when we get beyond that ultraviolet is ultraviolet energy damaging yes we know it is think about all the commercials for sunscreen that to protect our skin from ultraviolet rays x-rays when you get an x-ray think about it they put a lead vest over you to protect the rest of your organs and they only specifically hit a certain part of your body with those X-rays and then gamma would be the most damaging so you want to relate that to this information down here and look at the waves high energy high frequency means they have a short wavelength that would be gamma at the other end radio TV is down here we know TV waves don't bother us the frequencies coming from TVs light travel we're talking about light how fast does light travel well there's a constant it's called the speed of light it has the symbol C lowercase C you need to remember this number it's 3 times 10 to the eighth meters per second 3 times 10 to the eighth meters per second that's how fast light travels you want to make sure you write that down on your notes let's talk about some important vocabulary in this podcast electromagnetic radiation well what is it it's just the waves of energy on the bottom here I have a wave drawn let's talk about the different parts of the wave what's the amplitude well the amplitude is the height of the wave and you can see this right here would be your amplitude the symbol for amplitude is a lowercase a so I'm just going to write the symbols down here that's your amplitude wavelength is the length of the wave or the distance between two peaks and their corresponding Peaks the ones that are next to each other so this would be your wavelength this has a symbol that looks like this it's kind of like an upside down y it's called Lambda Greek symbol so you can see I draw it kind of backwards and then down like that that's the wavelength frequency the number of Peaks per second or waves per second that has a symbol it's called new it's kind of like a V it's pronounced new again another Greek I'll put little quotes around this these are Greek names for these letters frequency the number of wave Peaks per second and again the symbol is new it looks like a V if you're going to draw a v but you kind of curve it up like that the peak or the crest is the top of the wave so this would be called a peak or a Crest the trough is the bottom of the wave think about you've heard of trough before probably talking about pigs the pigs eat in a trough this would be the trough bottom of the wave let's talk about the relationship between frequency and wavelength so frequency number of Peaks or the number of waves per unit of time you can see here's two different waves this wave has a high frequency there's a lot of Peaks in the unit of time whereas compared to this one you can see there's only three high frequencies so let's look at the wavelength the wavelength is the distance between two corresponding Peaks so here's your wavelength I'll use the symbol again Lambda and here's your wavelength between this one high frequency would this be a shorter or longer wavelength be a shorter wavelength low frequency means we have a longer wavelength okay so they correspond in that aspect high frequency it takes a lot of energy to make these we have shorter wavelengths low frequency doesn't take a lot of energy to make these waves they have a longer wavelength something you want to remember is each color has a corresponding wavelength the color equals the wavelength so if you look at this visible spectrum I have down here look at the range here's your wavelength okay nanometers length right meter is the length well this is nanometers here's 400 where we mentioned this in the first slide notice it's violet here's 500 we're in the green range 600 we're in this orange yellowish range and then 700 were in the red range so take note the color corresponds to the wavelength if you have any questions you want to make sure you bring them to the attention of your teacher when you get to class thanks for your attention