Download Light and the Electromagnetic Spectrum: Chapter 13 - PAMS

Light and the Electromagnetic Spectrum: Chapter 13 and 14
Electromagnetic Waves
•Do NOT need matter in order to move
•Can travel through space (in a vacuum) where matter is not present
•Transfer energy between vibrating electric and magnetic fields
•The electric and magnetic waves are at right angles to the direction of the wave:
transverse waves
•Scientists describe them as both wavelike and particlelike
Production of the wave
•Electrons are needed to produce the wave, they change speed and direction as
they move in their orbits
•They also produce electric and magnetic fields that vibrate (move back and
forth)
•The speed of the waves is 300 million meters per second (the speed of light). It
takes light from the sun about 8 minutes to reach the Earth
The Electromagnetic Spectrum
•Arranged in order of wavelength and frequency
•Waves with the longest wavelength have the lowest frequency
•The spectrum ranges from very long wavelength, low frequency to short
wavelength, high frequency
•The amount of energy increases with frequency
•The only portion that is visible is light, the rest is invisible
1. Radio Waves
Longest frequency and lowest wavelength… not much energy
2. Produced when charged particles move back and forth in instruments
(antennae)
3. They transmit information from the broadcasting station to the antenna of
your radio or TV, AM (Amplitude Modulation) or FM (Frequency
Modulation)
4. Your TV uses AM waves for the picture and FM waves for the sound
5. Radio waves are also used in medicine. MRI (Magnetic Resonance
Imaging) shows pictures of body parts such as the brain
Microwaves
highest frequency radio waves
•Used for cooking food, microwaves pass through glass and plastic and are
absorbed by the food. Metals absorb microwaves and an electric current can
form.
•Radar: short wavelength microwaves, used to locate objects and monitor
speed… also used for communication (cell phones) because they are not easily
blocked by tree’s, mountains and buildings.
Infrared Waves
frequency lower than visible light
•Cannot be seen, but can be felt
•Warmer objects give off more heat than cooler objects
•Used to keep food hot, relieve sore muscles, dry hair
The Visible Spectrum
•Waves we can see: Red, Orange, Yellow, Green, Blue, Indigo, Violet
•Red has longest wavelength & Violet has shortest wavelength
•Is essential for photosynthesis
•Luminous object: anything that can give off its own light, produces its own light,
the sun
•Illuminated object: you can see it because it is lit up, the moon
Types of Light
•Incandescent Light: regular light bulb, light is produced from heat
•Fluorescent Light: bulb above you, produces little heat, energy efficient,
electrons pass through gas molecules
•Neon Light: Cool light, electrons pass through different gases producing
different colored light
Ultraviolet Rays
frequency higher than visible light
•Energy enough to damage and kill living cells
•UV lamps used to kill germs in hospitals
•Can be seen by insects and felt as sunburn on humans
•Cause your skin cells to produce vitamin D
X-Rays
•Frequency above ultraviolet
•Bones absorbs X-Rays which is why we can see the bones
•Overexposure can cause defects to cells.
Gamma Rays
•Most dangerous high frequency waves
•Can travel through 3 meters of concrete
•Used for cancer treatment
LIGHT
Mirror Types:
Concave mirror – a mirror that curves inward, if the image is close it is right side
up; if the image is farther away you see it upside down. Example: looking into a
spoon.
Convex mirror – the surface curves outward; the image is right side up and
smaller. Example: rear view mirror.
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When light strikes any form of matter, light is either transmitted, absorbed,
or reflected. We see any colors that have not been absorbed by the
object.
Transparent – where light goes through easily (glass, water, air…)
Translucent – transmits light but no details. (wax paper; frosted glass)
Opaque – when no light is transmitted. (wood, metal, etc…)
The Human Eye: Steps to sight
Light enters pupil
Goes through the Iris
Is refracted (by the cornea) and focused on the retina
The Lens focuses objects
Optic nerve goes to brain
Rods and Cones
•Rods: sensitive to light and dark
•Cones: responsible for seeing color, each cone is sensitive to a particular color.
•Colorblindness: when cones are not receptive to colors, most often red and
green, rare, but more common in males than females.
Types of sightedness
•Nearsightedness – a person can see things that are near but not things at a
distance.
•Farsightedness – a person can see things at a distance but not things that are
near.