Post on 18-Dec-2015
transcript
Electromagnetic Radiation
Waves… a reviewMost waves are either
longitudinal or transverse.Sound waves are longitudinal.But all electromagnetic waves
are transverse…
?
?
Electromagnetic Spectrum—name for the range of electromagnetic waves when placed in order of increasing frequencyRADIO WAVES
MICROWAVES
INFRARED RAYS
VISIBLE LIGHT
ULTRAVIOLET RAYS
X-RAYS
GAMMA RAYS
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?
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
Microwaves Wavelengths from 1 mm- 1 m Uses:
Microwave ovens Bluetooth headsets Broadband Wireless Internet Radar GPS
Infrared Radiation Wavelengths in between microwaves
and visible light Uses:
Night vision goggles Remote controls Heat-seeking missiles
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
Ultraviolet Shorter wavelengths than visible light Uses:
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
X-rays Tiny wavelength, high
energy waves Uses:
Medical imaging Airport security
Moderate dose can damaging to cells
Gamma Rays
Smallest wavelengths, highest energy EM waves
Uses Sterilizes medical equipment Cancer treatment to kill cancer cells
Kills nearly all living cells.
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 LightQuantum – 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)
) ) ) ) ) ) ) 1 2 3 4 5 6 7
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
ground state
excited state
Initial position
Final position
nucleus
Light & Energy5.1
) ) ) ) ) ) ) 1 2 3 4 5 6 7
nucleus
energy levels
Initial position
Final position
excited state
ground state
Light & Energy5.1
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!
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
Light & Energy5.1