Download Electromagnetic Waves transverse waves that consist of

Electromagnetic Waves
 transverse waves that consist of an electric-magnetic field
 Vary in wavelength and frequency not speed
 charged particles  electron – create electric or magnetic fields that vibrate. Ex. electrons moving back
and forth in an antenna create radio waves
 speed of all electromagnetic waves = 300 million meters/second in a vacuum. Ex. light from the Sun
travels to Earth in 8.3 minutes
Electromagnetic Spectrum
 The full range of frequencies of electromagnetic radiation is arranged on the EM spectrum
 electromagnetic waves are arranged in order of wavelength and frequency
Radio Waves
 Have the longest wavelength and the lowest frequency
(AM – amplitude modulation FM – frequency modulation)
 also used in medicine – MRIs
 microwaves – the highest frequency of all radio waves. Used for cell phones, weather forecasting & to
locate storms. Not as easily blocked by structures as radio waves.
 radar – radio detecting and ranging. Used to locate objects and monitor speed. Weather forecasts use
them to locate and track storms by recording the speed of reflected radar waves.
 -- Doppler effect
Infrared Waves
 cannot be seen but are felt as heat given off by all objects
Visible Light Waves
 Ranges b/w infrared and ultraviolet rays
 Visible Spectrum – almost ½ of Sun's energy is given off as visible light. Essential for photosynthesis
 (Roy G. Biv) prism - separates sunlight into the visible colors of the spectrum by refracting each
wavelength a different amount
Red = lowest frequency/highest wavelength
Violet = Highest frequency/lowest wavelength
Ultraviolet Waves
 cause your cells to produce Vitamin D.
 Tanning protects body from ultraviolet's harmful rays.
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X-rays
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Ozone layer protects by absorbing most of Sun's harmful ultraviolet rays.
energy of x-rays is great enough to pass easily through many materials (ex. skin) but denser materials
absorb (ex. bone). Can be used to diagnose medical problems
 Exploding stars give off most of their energy as X-rays
Gamma Rays
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Light
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EM waves with the highest frequencies and shortest wavelength.
Have the highest energy of the EM spectrum – can penetrate up to 3 meters of concrete
You see objects b/c light reflects off an object and into your eyes
Reflection  bouncing of light waves off a surface = mirror. Smooth surfaces reflect better than rough
surfaces  rough surfaces deflect waves in many ways instead of straight back to you (lake and throwing
stone in lake)
Mirrors  most are flat (like cosmetic mirrors) but some are curved (circus mirrors, spoon) – the wave
hits different places on the curve and bounces off in different directions = distorts the image – flat mirror
= waves bounce back straight toward you – doesn't distort image
concave mirror  curves like the inside of a spoon. Can be useful – headlights, flashlights or magnification
mirrors
convex mirror  curves like the outside of a spoon. Can also be useful – automobile rearview mirrors,
security and funhouse mirrors
Refraction – the bending of a wave as it moves from one medium to another light waves pass from air
to water which slow down once they hit the water. When the light waves hit the water they hit at an
angle and change speed = distorts image = light waves are refracted. Light waves also refract when they
pass from air  glass or plastic  lens
convex lenses  magnifying lens – make objects look bigger (microscopes, cameras, telescopes, far
sighted glasses)
concave lenses  helps you see far off objects – glasses for nearsightedness
most objects don't give off light – most are opaque = object that doesn't allow light to pass through (red
shoe absorbs all color except red = red shoe). Snow reflects all the light that hits it. White = presence of all
colors. Black = absence of all colors (space). Black absorbs all visible light
Color and Transmitted Light
 transparent objects (windows) transmit = allow light to pass through
 translucent objects (wax paper, frosted glass) – transmitted light is scattered producing a fuzzy image
How do you See?
 light enters the eye through an opening = pupil – the iris (colored area surrounding the pupil) controls the
amount of light that enters the pupil – the light entering the eye is refracted by the cornea and focused
on the retina (the image is upside down and smaller than the actual object) – the image is transferred to
and interpreted by the nervous system and brain. The retina contains nerve cells called rods and cones.
The lens makes adjustments for focusing on objects at different distances
 People wear glasses to see better b/c they bend light rays(refract) before they enter the eye so they
converge on the retina