hi this is teacher liz finally nara [Music] mojo one makes facilitated so lesson three is all about wavelengths and frequencies of electromagnetic waves objectives relate the wavelength and frequency of a wave identify the different regions of the electromagnetic spectrum and apply the basic wave equation in solving problems involving wavelength and frequency but first let's have a pre-test you know the drill this has five items with 10 second pause in between an inverse relationship means s1 increases the other decreases pause as frequencies increase on the electromagnetic spectrum wavelengths decrease pause radio waves have shorter wavelengths than ultraviolet rays paws all forms of electromagnetic waves can have varying speeds in a vacuum paws and gamma rays have the highest frequency and therefore contain photons with lowest energies pause please keep your answers near the end of this video lesson recall that in lesson 1 the following examples of em waves were introduced radio waves 3 times 10 raised to 8 meters per second or 300 000 kilometers per second in a vacuum visible well of course with the exception of superman x-ray vision the answer it's because electromagnetic waves have varying wavelengths and frequencies and because of this we have different forms of waves seven actually and you will get to know all of them in this lesson consider the following questions as you go along with this video lesson let's have question number one what is the relationship between wavelength and frequency of a wave let's recall from grade 7 science what wavelength and frequency are first suppose marantayung lubid at ginalonatin ito up and down to produce some waves as shown in the picture highest points are called crest lowest points are called trough and jung distance between two consecutive or makkasanudna crest and troughs wavelength on unit and wavelength i meter next is the frequency frequency is the number of waves that passes by a point in one second and on one cycle of a wave is the complete evolution of its shape until the point that it is ready to repeat itself so say example or waves the frequency of this wave is three waves per second or three hertz hertz is the unit of frequency so frequency at wavelength and relationship is at wavelength i inversely proportional to each other kapagmata's on frequency and wavelength an increase in one is a decrease in the other okay let's go to question number two what are the different regions of the electromagnetic spectrum the wide range of electromagnetic waves with different frequencies and wavelengths form the electromagnetic spectrum an electromagnetic spectrum and nahati sapitun parts note that there is no defining region for each form of electromagnetic waves advancing indirect values none frequencies and wavelengths as frequency increases wavelength decreases this means that radio waves have the longest wavelengths and gamma rays have the shortest but radio waves have the least frequency and gamma rays have the highest frequency among electromagnetic wave nato is photons are bundles or packets of wave energy a photons energy is directly proportional to frequency the higher the frequency the higher the photons energy from among the em waves gamma rays carry photons of high energies and frequency while radio waves have photons with the lowest energies frequency let's take a closer look at the regions of electromagnetic spectrum so radio waves are found at the longest wavelengths on the electromagnetic spectrum in a paramount broadcast on radio and television atang wavelength is from one centimeter to one thousand meter it can be as long as a football field microwaves are used in cooking radar telephone and other signals wavelength is from one tenth of a millimeter to one centimeter and can be the size of a penny or pinhead infrared radiation or infrared rays is what we describe as heat atom infrared rays thermal scanners in the bacteria visible light is the light that we can see and thus it is the only light detectable by the human eye anxiety is from 400 nanometer to 700 nanometer or the size of a virus next is the ultraviolet rays at the imagination coming from the sun and wavelength then raised to negative eight to ten raised to negative 10 meters or the size of a water molecule x-rays demand these are very energetic electromagnetic waves and are used in x-ray machines to take pictures of their bones alchemian wavelength i then raised to negative 10 meter to 10 raised to negative 12 acre or the size of an atom finally gamma rays these are the most energetic lightweights and are used in medicine to kill cancer cells honking in size i10 raised to negative 12 meter or the size of an atomic nuclear different forms of electromagnetic waves is a mnemonic device always remember rabbits marry in very unusual expensive gardens and demonic device nato i according to increasing frequency or decreasing wavelength and so the third question is what is the basic wave equation a basic wave equation is state now relationship among wave speed frequency and wavelength naritan canyon formula where v is the velocity and is equal to 3 times 10 raised to 8 meters per second which is the speed of light in vacuum the greek latter lambda which represents the wavelength n is expressed in meters and f for frequency expressed in hertz or one over s or s raised to negative one sample problems for the basic wave equation problems that all let's assume that electromagnetic waves travel in vacuum first what is the wavelength of light waves with a frequency of 6 times 10 raised to 14 hertz and given that then v is equal to 3 times 10 raised to 8 meters per second and that is constant the speed of light f is equal to 6 times 10 raised to 14 hertz let's find the lambda or the wavelength for the solution we write first the formula v is equal to f lambda and we need to derive an equation for lambda because that is what we are looking for divide both sides of the equation by f so we can cancel f on the other side and we arrive with lambda is equal to v over f then we substitute the values 3 times 10 raised to 8 meters per second for velocity over 6 times 10 raised to 14 s raised to negative 1 for frequency performing the operation 3 divided by 6 is 0.5 8 minus 14 is negative 6 and cancelling second so um the unit is metered simplifying that is 5 times 10 is negative 7 newton that's our final answer next what is the frequency of radio waves with the wavelength of 20 meters and given that then again speed of light is equal to 3 times 10 days to 8 meters per second and then the lambda or the wavelength which is equal to 20 meters or quick converge not into scientific notation 2.0 times 10 raised to 1 meter now let's find the frequency so our formula again is b is equal to frequency times lambda we derive an equation for frequency because that's what we are looking for so we start our formula divide both sides by lambda our formula now becomes f is equal to v over lambda and substitute the values and perform the operation 3 divided by 2 is 1.5 minus one is seven the unit is over s or over second and that is hertz so our final answer is one point five times ten raised to seven hertz now let's talk about the refraction of electromagnetic waves where the speed of the am wave travels is lower when it encounters a medium so electromagnetic waves move slower in different media when traveling through a material medium electromagnetic waves retain their frequency but their speed and wavelength changes according to the basic wave equation if the speed of electromagnetic wave decreases the wavelength or the distance between two successive points must decrease too or must magically uncannily wavelength but the frequency remains the same now here's a question for your reflection log what happens to the wavelength of the electromagnetic wave if its frequency increases take a three minute pause and now the posters arrange the following forms of electromagnetic waves according to increasing wavelength take a two minute pause next arrange the following forms of electromagnetic waves according to increasing frequency take a two minute pause finally solve the following problem what is the frequency of a microwave that has a wavelength of 1.5 times 10 raised to 2 meters take a 3 minute pause okay [Music] pretest [Music] all right up next module two practical applications of electromagnetic waves stay tuned for the next module marami salamat for allah