Part 1 Electromagnetic Waves Transverse wave with alternating

Part 1: Electromagnetic Waves

Transverse wave with alternating electric and magnetic fields at right angles to each other.

Light also behaves like a particle (called a photon) Duality—both particle-like and wave-like behavior. Light behaves as both matter AND energy

Light waves are a form of Radiation: -Energy transmitted without need for a physical connection between the two locations (a medium)

Einstein defined speed of light as a constant. Speed of light in a vacuum: c=3 x 8 10 m/s

Different forms of light energy: Radio waves, Microwaves, Infrared, Visible Light, Ultraviolet, X-rays, and Gamma Rays Organized into the Electromagnetic Spectrum by frequency, wavelength, and energy.

http: //www. brainpop. com/science/energy/electromagneticspectrum/

Relationship between frequency and energy f

RADIO WAVES • longest wavelengths and lowest frequencies of all electromagnetic waves. Radio stations Each broadcasts at a different frequency Tuner on your radio dial adjusts to match frequency of station – # on radio dial tells frequency – radio picks up radio waves through an antenna and converts it to sound waves.

MRI (MAGNETIC RESONANCE IMAGING) – Uses Short-wave radio waves with a magnet to create an image MRI of the Brain

MICROWAVES • Microwaves—shortest wavelengths and the highest frequencies of the radio waves. – Used in microwave ovens. • Waves transfer energy to the water in the food causing them to vibrate which in turn transfers energy in the form of heat to the food. – Used by cell phones and pagers. – RADAR (Radio Detection and Ranging) • Used to find the speed of an object by sending out radio waves and measuring the time it takes them to return.

INFRARED RAYS • Infrared= “below red” • Shorter wavelength and higher frequency than microwaves. • Given off by objects as heat energy Ex. Heat lamps. • Thermogram—a picture that shows regions of different temperatures in the body.

VISIBLE LIGHT • Shorter wavelength and higher frequency than infrared rays. • Electromagnetic waves we can see • Longest wavelength= red light • Shortest wavelength= violet (purple) light • White light is a combination of all wavelengths • When light enters a new medium it bends (refracts). Each wavelength bends a different amount allowing white light to separate into it’s various colors ROYGBIV.

White Light

ULTRAVIOLET RAYS • Shorter wavelength and higher frequency than visible light • Used to kill bacteria. (Sterilization of equipment) • Causes your skin to produce vitamin D (good for teeth and bones) • Used to treat jaundice (in some new born babies. • Too much can cause skin cancer. • Use sun block! to protect against UV rays

X- RAYS • Shorter wavelength and higher frequency than UVrays • Carry a great amount of energy • Can penetrate most matter. • Bones and teeth absorb x-rays. (The light part of an x-ray image indicates a place where the x-ray was absorbed) • Too much exposure can cause cancer – (lead vest at dentist protects organs from unnecessary exposure) • Used by engineers to check for tiny cracks in structures. – The rays pass through the cracks and the cracks appear dark on film.

GAMMA RAYS • Shortest wavelength and highest frequency • Carry the greatest amount of energy and penetrate the most. • Used in radiation treatment to kill cancer cells. • Can be very harmful if not used correctly.

-Analysis of the way in which atoms absorb and emit light

As electron falls back down, it emits (or releases) a photon of light Electron absorbs a photon and jumps up to a higher energy level.

Emission Spectra – light frequencies being emitted (bright lines/ black background)

Absorption Spectra – light frequencies being absorbed (bright background/ black lines)

> Photons emitted make an emission line > Photons absorbed as they hit an atom make an absorption line

The same gas will have emission and absorption lines in the same place

Unique for each element… like fingerprints…

Doppler Effect – wavelength and frequency change when the source of a wave is moving or observer is moving

Blue Shift – wave is compressed (moving closer) Red Shift – wave is expanded (moving away)