energy Waves do not have energy, they transmit energy Definitionthe ability to do work Symbol E Units Joules, abbreviate J
Speed Definitiondistance that an object moves per unit of time Symbol c Units m/s
Electromagnetic (EM) waves travel in a vacuum (not a vacuum cleaner…vacuum means “space that is empty of matter”); they do NOT need a medium (like air or water) to travel through travel at the speed of light
Electromagnetic Spectrum the range of all possible frequencies of electromagnetic radiation
Red Martians Invaded Venus Using X-ray Guns Radio Micro Infrared Visible Ultraviolet X-ray Gamma
Visible light ranges in wavelength from approximately 400 nm (4 x 10 -7 m) to 700 nm (7 x 10 -7 m). Acts as a wave and a particle (photon) Each color has a unique wavelength, energy, and frequency range Makes the colors of the rainbow ROY G BIV
low energyhigh energy low amplitude high amplitude
Relationships Frequency ( ) and Wavelength ( ) – inverse Formula for speed demonstrates this relationship… c = c = speed of light = 3.00 x 10 8 m/s = frequency (Hz) = wavelength (m)
Practice Problem What is the wavelength of a radio wave with a frequency of 1.01 x 10 8 Hz?
Practice Problem An X-ray has a wavelength of 1.15 x 10 -10 m. What is its frequency?
Relationships Frequency and Energy - direct Max Planck discovered this: – Electromagnetic radiation is emitted in small bursts, called "quantum“ Think of a “quantum” as a packet of a specific amount – Each burst (quantum) has energy that depends on the frequency E = h is the mathematical formula that relates light and energy E = energy, measured in Joules (J) h represents Planck’s constant h = 6.626 x 10 -34 Js = Frequency, measured in Hertz
Practice problem What is the energy of radiation with a frequency of 6.32 x 10 20 Hz?
http://blogs.timesofindia.indiatimes.com Why do fireworks burn with different colors?
Fireworks contain metallic salts. Each metal will emit a different color when vaporized. http://williamcraigcook.com/fireworks/DiffColors.jpg
http://www.sciencephoto.com Why do fireworks burn with different colors? http://www.webexhibits.org Photons (particle of light) are emitted from an atom when electrons move from a higher potential energy level to a lower potential energy level
Why do fireworks burn with different colors? http://williamcraigcook.com/fireworks/DiffColors.jpg The relative frequency, wavelength and energy of the photon is associated with the color of light emitted.
Bohr Model Electron in an Atom hyperphysics.phy-astr.gsu.edu Hydrogen atom absorbs energy equal to the energy of the photon of violet, blue-green and red light. This causes the hydrogen electron to move from its ground state to an excited state. The electron returns to its ground state and releases energy resulting in the emission spectra.
Ground state vs. Excited State Electrons Absorption of Energy Release of Energy (Emission) hyperphysics.phy-astr.gsu.edu
Electrons and Light Quantum Leap When a valence electron absorbs energy (from heat or electricity), it “jumps” to a higher energy level (excited state). This jump is called a quantum leap. It is unstable at this excited state and cannot stay there. When is light emitted? When it falls back to a stable energy level (ground state), it releases the energy it previously absorbed. This energy is emitted as a photon of light.
Atoms and Photons and Color Each atom’s electrons “jump” to certain excited states. Each “fall” releases a photon of a certain energy, frequency, and wavelength which correspond to colors of light. ATOMIC EMISSION SPECTRUM: the colors of light emitted by an atom’s electrons, and it can be used to identify the element.