Electromagnetic Radiation http://www.jessb.org

Waves… a review Most waves are either longitudinal or transverse. Sound waves are longitudinal. But all electromagnetic waves are transverse…

? ? Prompt students to guess what the teal box, then the blue box, is hiding. (Wavelength, Amplitude)

Electromagnetic Spectrum—name for the range of electromagnetic waves when placed in order of increasing frequency GAMMA RAYS ULTRAVIOLET RAYS RADIO WAVES INFRARED RAYS X-RAYS MICROWAVES VISIBLE LIGHT

Electromagnetic waves Produced by the movement of electrically charged particles Can travel in a “vacuum” (they do NOT need a medium) Travel at the speed of light c= 3.0 x 108 m/s Also known as EM waves

What is the relationship between frequency and wavelength What is the relationship between frequency and wavelength? INVERSE (as one goes up, other goes down)

Radio waves Longest wavelength, lowest energy Uses: TV broadcasting AM and FM broadcast radio Heart rate monitors Cell phone communication MRI (MAGNETIC RESONACE IMAGING) Uses Short wave radio waves with a magnet to create an image Click the little rainbow box in the top right corner to return to the overview EM spectrum diagram

Microwaves Wavelengths from 1 mm- 1 m Uses: Microwave ovens Bluetooth headsets Broadband Wireless Internet Radar GPS Click the little rainbow box in the top right corner to return to the overview EM spectrum diagram

Infrared Radiation Wavelengths in between microwaves and visible light Uses: Night vision goggles Remote controls Heat-seeking missiles Click the little rainbow box in the top right corner to return to the overview EM spectrum diagram

Visible light Only type of EM wave able to be detected by the human eye Violet is the highest frequency and energy light Red light is the lowest frequency light and lowest energy Click the little rainbow box in the top right corner to return to the overview EM spectrum diagram

Ultraviolet Uses: Shorter wavelengths than visible light Black lights Security images on money Harmful to living things Used to sterilize medical equipment Too much causes sun burn Extremely high exposure can cause skin cancer There is one more UV slide…

X-rays Uses: Tiny wavelength, high energy waves Medical imaging Airport security Moderate dose can damaging to cells Click the little rainbow box in the top right corner to return to the overview EM spectrum diagram

Gamma Rays Uses Smallest wavelengths, highest energy EM waves Sterilizes medical equipment Cancer treatment to kill cancer cells Kills nearly all living cells. Click the little rainbow box in the top right corner to return to the overview EM spectrum diagram

Waves or Particles Electromagnetic radiation has properties of waves but also can be thought of as a stream of particles. Example: Light Light as a wave: Light behaves as a transverse wave which we can filter using polarized lenses. Light as particles (photons): When directed at a substance light can knock electrons off of a substance (Photoelectric effect)

Emission of Light Quantum – minimum amount of energy that can be gained or lost by an atom; can be referred to as a packet of energy Photon – packet of light energy (quantum)

Electrons & Light ) ) ) ) ) ) ) 1 2 3 4 5 6 7 energy levels 5.1 Light & Energy Electrons & Light As energy is absorbed, the electrons move from their ground state (original energy level) to an excited state (higher energy level) energy levels Initial position Final position ) ) ) ) ) ) ) 1 2 3 4 5 6 7 nucleus excited state ground state

Electrons & Light ) ) ) ) ) ) ) 1 2 3 4 5 6 7 energy levels 5.1 Light & Energy Electrons & Light Electrons are unstable in their excited state, so they return to the ground state by releasing energy. During this return, light is emitted! energy levels Final position Initial position ) ) ) ) ) ) ) 1 2 3 4 5 6 7 nucleus excited state ground state

5.1 Light & Energy Spectra of Light Emission Spectra - A set of frequencies of the electromagnetic waves emitted by atoms of the element Shows all the wavelengths of light that are emitted Spectroscope – instrument used to see the emission spectra Unique to each element