Electromagnetic Radiation

Waves… a reviewMost waves are either

longitudinal or transverse.Sound waves are longitudinal.But all electromagnetic waves

are transverse…

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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