[Music] hello students welcome to great and science lesson and i'm your teacher mom marian soriano [Music] did you call somebody today using your smartphone did you listen to your favorite radio station [Music] or have you tried cooking your food with a microwave oven [Music] did you know that all these human activities calling someone using your smartphone tuning to your favorite radio station cooking food in a microwave oven have one all in common they all use electromagnetic waves or em waves lesson one introduction to electromagnetic waves you have learned from the previous lessons in science that waves are temporary disturbance that transfer energy from one place to another there are two important ways on how energy is transported in the world around us we have mechanical waves and electromagnetic waves what are the differences of these two remember from your previous lessons in science waves in water and sound waves in air are two examples of mechanical waves matter such as solid liquid gas or plasma that mechanical waves are traveling through is called a medium while on the other hand electromagnetic waves such as visible light differ from mechanical waves in that they do not require a medium to propagate or to transfer energy this means that electromagnetic waves can travel not only through air and solid materials but also through a vacuum space how are em waves formed electromagnetic waves are formed when an electric field comes in contact with a magnetic field [Music] electricity and magnetism can be static but changing magnetic field will induce electric field and vice versa these changing fields form electromagnetic waves always keep in mind that the electric field and magnetic field of an electromagnetic wave are perpendicular or at right angles to each other remember also that electric field and magnetic field are also perpendicular to the direction of the em wave's energy always remember that electromagnetic waves travel with a constant velocity or speed of 3 times 10 to the power of 8 meter per second in vacuum space em waves are deflected neither by the electric field nor by the magnetic field however they are capable of showing interference or diffraction em waves are considered to be transverse waves to understand further the behavior of em waves here are some characteristics of waves that you need to remember we have the amplitude which is the height of a wave and usually measured in meters remember also that amplitude of a wave is associated to the amount of energy a wave is carrying another wave characteristic is wavelength which is the distance between two consecutive grass or trough and usually measured in meters next is frequency which is the number of waves passing a point in a certain time we normally use a time of 1 second so this gives frequency the unit hertz since 1 hertz is equal to 1 wave per second let's have practice exercise study these two waves which wave has higher frequency you are correct wave b has higher frequency than wave a let's have another one which wave has longer wavelength again you are correct wave a has longer wavelength than wave b let's continue our lesson remember also that all electromagnetic waves travel at the same speed which is about 3 times 10 to the power of 8 meter per second through a vacuum as you further understand our lesson on em waves please take note of the following wave equation electromagnetic waves obey the following wave formula this triangulation method will help you remember the wave equation which is wave speed is equal to frequency times wavelength let's have an example problem using the wave equation an em wave has wavelength of 4.0 meters in a vacuum space what is the frequency of the em wave first let's identify the given the given r the wavelength which is 4.0 meters and the speed of light which is 3.0 times 10 to the power of 8 meter per second we are looking for the frequency of the em wave for the equation we will be using the wave equation let's have our solution first we need to derive the equation needed to find the answer the derived equation is frequency is equal to speed of light over wavelength now we can substitute the values the answer is 75 million hertz or 75 megahertz there are different types of em waves we have radio waves microwaves infrared visible light ultraviolet x-rays and gamma rays these em waves can be split into range of frequencies or wavelength this is known as the electromagnetic spectrum examine the electromagnetic spectrum chart starting from radio waves to gamma rays compare the frequency and wavelength of em waves did you notice as you move from left to right of the electromagnetic spectrum the wavelengths get smaller and the frequencies get higher furthermore there is an inverse relationship between wavelength and frequency which simply means as one goes up the others goes down electromagnetic waves can be described in terms of a stream of massless particles called photons it's traveling in a wave-like pattern at the speed of light each photon contains a certain amount of energy the different types of em waves are defined by the amount of energy found in the photons observe that energy goes up as the frequency increases the energy is directly proportional to the frequency here is an example radio waves have photons with low energies microwave photons have a little more energy than radio waves infrared photons have still more likewise with the order of colors of visible light they are arranged from lowest to highest frequency red has the lowest energy and frequency while violet has the highest energy and frequency lastly we have the most energetic of all em waves and has the highest frequency but has the shortest wavelength the gamma rays em waves can be classified as ionizing or non-ionizing form of hydration non-ionizing radiation is the part of the electromagnetic spectrum where there is insufficient energy to cause ionization this includes radio waves microwaves infrared visible light and ultraviolet while on the other hand we have the ionizing radiation it is a type of energy released by atoms that travels in the form of electromagnetic waves this includes gamma rays or x-rays ionizing aim waves are more dangerous to humans than non-ionizing we'll further discuss about this in our next lesson always keep in mind that the electromagnetic spectrum is a continuum of all electromagnetic waves arranged according to frequency and wavelength [Music] let's perform an activity get a piece of paper a pen and a ruler you may pause the video as you answer the activity [Music] let's start [Music] draw the blank electromagnetic spectrum chart in your paper complete the chart by arranging the different types of em waves [Music] let's check your answer starting from the lowest frequency or longest wavelength to the highest frequency or shortest wavelength we have range waves followed by microwaves we have infrared for the visible colors of light we have red orange yellow green blue indigo and violet beyond visible light we have ultraviolet next we have x-rays and lastly gamma-ray [Applause] to summarize what you have learned electromagnetic waves or em waves are waves that are created as a result of vibrations between an electric field and a magnetic field electromagnetic waves can be expressed in terms of energy speed wavelength or frequency frequency is measured in cycles per second or hertz wavelength is measured in meters [Music] em waves travel with a constant speed of 3 times 10 to the power of 8 meter per second in vacuum the larger the frequency of an em wave the smaller the wavelength and vice versa the frequency of an em wave is directly proportional to energy you also learn the higher frequencies of em hydration consisting of x-rays and gamma rays are types of ionizing radiation lower frequency radiation consisting of ultraviolet or uv infrared microwaves and radio waves are types of non-ionizing radiation the electromagnetic spectrum includes from longest wavelength to shortness radio waves microwaves infrared visible light ultraviolet x-rays and gamma rays i hope you enjoyed our lesson this is mom marian soriano see you in the next lesson [Music] you