STUDIO UNIT 16PHY 2054 College Physics IIDrs. Bindell & Dubey1ELECTROMAGNETICWAVESObjective: To Understand Electromagnetic WavesEnergy is transported to us from the sun via a class of waves known as electromagnetic waves. The fundamental sources of all electromagnetic radiation are electric charges in accelerated motion.All objects emit electromagnetic radiation as a result of thermal motion of their molecules; this radiation,called thermal radiation, is a mixture of different wavelengths.Unlike mechanical waves, which need the oscillating particles of a medium such as water or air to betransmitted, electromagnetic waves require no medium. What’s “waving” in an electromagnetic wave arethe electric and magnetic fields. Scottish physicist James Clerk Maxwell (1831-1879) showed that thesetwo fields fluctuating together can form a propagating electromagnetic wave.The speed of an electromagnetic wave in a vacuum is: c = 3 x 108 m/s.An electromagnetic wave is a transverse wave because the electric and magnetic fields are bothperpendicular to the direction in which the wave travels.2An electromagnetic wave, like any periodic wave, has a frequency f and a wavelength λ that are related to the speed v of the wave by v = f λ. For electromagnetic waves traveling through a vacuum or, to a good approximation, through air, the speed is v = c, so c = f λ. As shown in the following figure, electromagnetic waves exist with an enormous range of frequencies. The ordered series of electromagnetic wave frequencies or wavelengths is called the electromagnetic spectrum.In electromagnetic waves, the energy is carried by the electric and the magnetic fields that comprise the wave. The total energy density u of an electromagnetic wave in a vacuum is the sum of electric energy density and magnetic energy density: 3222121Volumeenergy TotalBEuoo- Based on the fact that in an electromagnetic wave propagating through a vacuum or air, the electricand magnetic field carry equal amounts of energy per unit volume of space, derive two additionalequations for the total energy density. u = ________________ and u = ___________________- Based on the fact that in an electromagnetic wave propagating through a vacuum or air, the electricand magnetic field carry equal amounts of energy per unit volume of space, derive a relationbetween the magnitudes of the electric and magnetic fields in an electromagnetic wave.As an electromagnetic wave moves through space, it carries energy from one region to another. This energy transport is characterized by the intensity of the wave. For an electromagnetic wave, the intensity is the electromagnetic power divided by the area of the surface4tAEnergyTotalSorAPScutAuctAAtAPS energy TotalThus, the intensity and the energy density are related by the speed of light, c. - Write three equations for intensity S in terms or electric and magnetic fields. - What is the SI unit of intensity?PolarizationIn a polarized light, the electric field fluctuates along a single direction. An unpolarized light consistsof short bursts of electromagnetic waves emitted by many different atoms. 5cuS Polarized light may be produced from unpolarized light with the aid of polarizing material (Polaroid). Such materials allow only the component of the electric field along one direction to pass through, while absorbing the field component perpendicular to this direction. The direction ofpolarization that a polarizing material allows through is called the transmission axis. It does not matter how the transmission axis is oriented, the average intensity of the transmitted polarized lightis one-half the average intensity of the incident unpolarized light.As shown in the following figure, two sheets of polarizing material, called the polarizer and the analyzer are used to adjust the polarization direction and the intensity of the light. This can be achieved by adjusting the angle θ between the two polarizing materials.When linearly polarized light strikes a polarizing filter, the intensity of the transmitted light is given by Malus’ Law. 62cosoSS - Using the relationship between intensity and total energy density, s = cu, derive the equation for Malus’ law.Experiment: PolarizationEQUIPMENT NEEDED:Optical Bench -Light Source, Polarizers (2), Component Holders (3), Crossed Arrow TargetYour optics equipment includes two Polarizers, which transmit only light that is plane polarized along theplane defined by the 0 and 180 degree marks on the Polarizer scales. Light that is polarized along anyother plane is absorbed by the polaroid material. Therefore, if randomly polarized light enters thePolarizer, the light that passes through is plane polarized. In this experiment, you will use the Polarizers toinvestigate the phenomena of polarized light.7ProcedureSet up the equipment as shown in the above figure. Turn the Light Source on and view the Crossed Arrow Target with both Polarizers removed. Replace Polarizer A on the Component Holder. Rotate the Polarizer while viewing the target.1. Does the target seem as bright when looking through the Polarizer as when looking directly at the target? Why?2. Is the light from the Light Source plane polarized? How can you tell?8Align Polarizer A so it transmits only vertically polarized light. Replace Polarizer B on the other Component Holder. Looking through both polarizers, rotate Polarizer B.3. For what angles of Polarizer B is a maximum of light transmitted? For what angles is a minimum of light transmitted?4. If the intensity of the light falling on polarizer A is S, (a) what is the intensity of the light coming out of polarizer A?(b) what is the intensity of the light coming out of polarizer B?9Additional Questions5. A beam of unpolarized light of intensity I0 passes through a series of ideal polarizing filters withtheir polarizing directions turned to various angles as shown in the figure.(a) What is the light intensity (in terms of I0) at points A, B and C?(b) If we remove the middle filter, what will be the light intensity at point C?6. For each of the three sheets of the polarizing material shown in the drawing, the orientation of thetransmission axis is labeled relative to the vertical. The incident beam of light is unpolarized and hasan intensity of 1260.0 W/m2. What is the intensity of the