Chapter 22 Nature of Light
KEY
BrainPops – EM Spectrum, colors, Refraction/Diffraction, Light
Vocabulary
Light Waves
Radiation
Interactions: Light Wave Velocity
Electromagnetic Spectrum
Radio Waves
Explanation
A wave that the energy moves
perpendicular to the direction of the
wave ( type of TRANSVERSE wave)
that does not require MEDIUM to
move the energy (called an
ELECTROMAGNETIC wave)
Drawing/Examples
Travel in straight lines until striking an
object
The emission of energy in the form of
ELECTROMAGNETIC waves
Through a near – vacuum =
300,000,000 m/s
All electromagnetic radiation travels
at the speed of visible light, but have
different wavelengths
All light waves!
The range of light waves from longest
to shortest WAVELENGTH (lowest to
highest FREQUENCY)
Lowest energy and LONGEST
wavelength/LOWEST frequency of EM
waves
Ships can use radio waves like sonar
Microwaves –
patented by American Engineer
Percy Spencer in 1945
Infrared Light Waves
Carry more energy than radio waves,
but less than infrared waves
Infra means BELOW
Emitted by the SUN
Directly below first color we can see
on the visible spectrum
A very small part of the EM Spectrum
and a form of RADIANT energy
Visible Light
Ultraviolet Light Waves
UV color changing shirts or nail polish
X Rays
Ultra means ABOVE
Emitted by the SUN
Can be useful or harmful
More energy than visible light waves,
so directly after the last color we can
see on the EM spectrum
Penetrates the skin without being
absorbed by the BONE
Why do you see lightening before you
hear thunder?
Light travels faster than sound… light
@ 300,000 km/s and sound @
343 m/s (takes 8 min for sunlight to
hit earth)
(complete separate chart of spectrum)
Examples: baby monitors, ham radio,
CB, cordless phones, walkie talkies
Cell phone waves
Radio station waves
Satellite cable tv signals
Examples: microwave
Radar for airplanes/ships
Police officers
Heat lamps
Feel warmth from the sun (thermal
from fire)
Infrared camera (thermal imaging)
List the colors we can visibly see in
order from lowest to highest
frequency: RED, ORANGE, YELLOW,
GREEN, BLUE, INDIGO, VIOLET
Useful: kills bacteria, allows body to
produce Vitamin D, Black lights
Harmful: sunburn, skin cancer,
wrinkles, eye damage
Security for ID’s to look for fakes
Wear metal shield over other parts of
body to shield from the high energy
waves
Gamma Rays
Highest energy and SHORTEST
wavelength/ HIGHEST frequency of
EM waves
Law of Reflection
Angle of INCIDENCE = the angle of
REFLECTION
Diagram:
Absorption
Transfer of ENERGY carried by light
waves to particles of MATERIAL
Feel warmth?
(Spectrophotometer Lab)
Why the sky is BLUE
Interactions: Diffraction
of visible light
The release of light ENERGY by
particles of matter that have absorbed
energy
The bending of the wave due to
moving from one medium to another,
which is caused by the VELOCITY of
the wave in the new medium
Light waves strike an object and new
waves are produced (go around the
barrier)
Interactions: Reflection
of visible light
The BOUNCING BACK of the light
wave
Scattering
Interactions: Refraction
of visible light
Interactions: Interference
of visible light
Why you can see across a room by
looking in a mirror or other reflective
surface
Rainbows
Why doesn’t light diffract well?
Usually absorbed and doesn’t bend
well… ex: parking lot lights flood the
parking lot, but if you go around to
the other side of a building, the light
doesn’t bend around the side of the
bldg
BUT, SOUND diffracts well… sound in
locker down & into classroom
Mirrors/Glass/smooth surfaces such
as lakes & ponds
Two or more waves OVERLAP and
combine as a result of DIFFRACTION
Brighter with more light waves
The passing of light THROUGH matter
Transparent – Light PASSES
THROUGH EASILY - CLEAR
Translucent – SCATTERS LIGHT AS IT
PASSES THROUGH - WAX PAPER
Opaque – DOES NOT TRANSMIT
LIGHT
Why do we wear dark color clothes in
winter and lighter color clothes in
summer? (absorption/reflection)
Transmittance / Transmission
Colors
Useful to medical profession:
surgery = gamma knife
kill cancer cells
gamma camera
(“Bear Lab”)
WHITE = all the colors of light
reflected
BLACK = all colors absorbed
Specific colors = the specific color you
“see” is being REFLECTED and all
others are ABSORBED