Download The Electromagnetic spectrum and light

The Electromagnetic spectrum and light
Electromagnetic Radiation
• Electromagnetic waves: are transverse waves
produced by the motion of electrically charged
particles.
• They do not need a medium and travel in
straight lines.
• Speed- Can travel though empty space at
300,000km/s or 186,000 miles/sec
• Radiation:The transfer of energy by
electromagnetic waves.
• Photons: Bundles of light energy produced by
electron movement
Radio Waves
• All around us
• Long wavelengths and low
frequencies.
• Radio, TV, cellular phones,
cordless phones,
Microwaves
• Radio waves with the highest
frequency and energy.
• Communications and
microwave ovens!
Infrared Radiation
• Slightly lower frequency than
visible light.
• Felt as heat
• Infrared lamps keep your french
fries warm!
IR does not
penetrate walls
and so does not
interfere with other
devices in
adjoining rooms.
Infrared is the
most common way
for remote controls
to command
appliances.
Visible Radiation (Light)
• Or light, is the only part of the electromagnetic
spectrum you can see!
• Light Energy is produced by the activity of
electrons around the nucleus of an atom.
• Each different wavelength of light has a
different color!!
Ultraviolet Radiation
• Higher frequency than visible light.
• Greater penetrating power!
• Helps skin cells produce vitamin D, which
is needed for healthy bones and teeth!
• Sterilize surgical instruments
• Over exposure kills healthy cells!!!
• Sagging, dry skin, skin cancer!
• Sunblock and sunglasses!!!
X Rays
• X rays have a shorter wavelength and a higher frequency
then ultraviolet radiation.
• Higher energy allows X rays to travel
through some types of matter such as
your skin and muscles.
Gamma Rays
• Have the highest frequency and are
the most penetrating of
electromagnetic waves!
• They are emitted from the nuclei of
radioactive atoms.
• Earth receives some from space.
• Can be used to kill cancer cells.
Electrons
• Electrons moving to a higher level gain
energy
• Electrons that move to a lower level give
off electromagnetic energy
• Electricity is the movement of electrons,
so it comes from the atom.
Light Theories
• Wave Theory (like dropping a pebble into a pond)
•
•
Electromagnetic
Particle
• Wave Particle Duality (modern Light Theory)energy of the photon is proportional to its
frequency
Transverse Waves
Mount Moran in Jackson,
Wyoming
Properties of light
•
•
•
•
•
•
•
•
Luminous- give off their own light (candle)
Illuminated- light reflects off of it (moon)
Transparent- See through
Translucent- Partially see through (blurry)
Opaque- not see through (us)
Reflection- Light bounces off
Refraction- light bends going through
Absorption- light that gets absorbed in the
material.
Types of Reflection
• Reflected light is when light is not
completely absorbed by an object.
• The type of surface affects the type of
reflection.
• Regular reflection- smooth surface,
forms a clear image. (flat mirror)
• Diffuse reflection- rough surface, forms
a fuzzy image.
Reflections
• You need 2 things for a reflection:
1. Light
2. A smooth surface
3. The Law of reflection- the angle of reflection
is equal to the angle of incidence .
(Only applies to smooth surfaces, not rough)
MIRRORS (3 Types)
• 1. Plane Mirror-
or flat mirror
creates a virtual
image- image
that is right-side
up and the same
size.
MIRRORS
• 2. Concave mirrormirror with a surface
curved inward.
• concave mirrors can
form either virtual
images or real
images depending on
the position of the
object in relation to
the focal point.
• 3. Convex mirrors- a mirror
with a surface that curves
outward.
• The rays spread out but
appear to come from a focal
point behind the mirror.
• Images formed are always
virtual since the reflected
rays do not meet.
• Because you can see more
through convex mirrors, the
images always appear
smaller and farther away
“objects seen in the mirror
are closer than they appear”
MIRRORS
LENSES
• A lens is a curved piece of glass
that is used to refract light
• Convex- thin on top and bottom, thick
in the middle
• Concave- thick on top and bottom,
thin in the middle
A corrective lens is a lens worn on or
before the eye, used to treat myopia,
hyperopia, astigmatism, and
presbyopia. The most common types of
corrective lenses are eyeglass lenses
and contact lenses. Intraocular lenses
are also beginning to become common.
Myopia (near sightedness) requires
biconcave or diverging lenses,
whereas hyperopia (far sightedness)
requires biconvex or converging
lenses.
Correct sight with concave
lens
Lens is to convex
• The image is focused in
front of the retina
• Recall: convex lens focus
light (the more convex, the
quicker the focus)
• Adding glasses with
concave lens will spread
light out and not let it focus
so quickly
Correct sight with convex
lens
Lens to concave
• People far sighted see things
far well, but do not see
things near very well
• Recall: concave lens spreads
light out
• So,
• Adding glasses with convex
lens will focus light more
and not so spread out
Image formation
• The image through a convex
lens appears upside down
• The image through a
concave lens spreads out the
light rays