Light
Light
•Is a form of energy
•Behave as an electromagnetic wave
•Have both electrical and magnetic
properties
•Can travel through empty space
•Are made up of tiny particles or energy
called photons
•Unless disturbed, photons travels in
straight lines.
Electromagnetic Spectrum
• Range of waves or small parts of light waves
that make a electromagnetic spectrum( Large
band of waves)
• Energy of a wave is related to its wavelength
and its frequency.
Visible Light Waves
*The longer wavelength, lower frequency regions
*The shorter wavelength, higher frequency regions
The Electromagnetic Spectrum
Electromagnetic waves
• Visible light waves are the only
electromagnetic waves we can see
• Each color has a different wavelength
• Red has the longest wavelength
• violet has the shortest wavelength.
• When all the waves are seen together, they
make white light.
Creating a rainbow.
What are electromagnetic waves ?
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Radio waves
microwaves,
Infrared
Ultra Violet
x-rays
TV
radio transmissions
Gama rays
Radio Communication cont’d.
• Television
– Sound by FM; picture components by AM
• Telephones
– Microphone converts sound waves into an
electrical signal
– In cell phones, current creates radio waves
transmitted to and from a microwave tower
– Cordless and cell phones are transceivers that
transmit one radio signal and receive another
from a base unit
• Global Positioning System (GPS)
– Uses multiple satellites, monitoring stations, and
receivers to determine location
Electromagnetic Spectrum cont’d.
• Radio waves
– Longest wavelength, lowest frequency, sound;
radar; magnetic resonance imaging (MRI)
• Microwaves
– Communication, microwaves interfere with the
water molecules in food causing more friction
• Infrared
– Transmits thermal energy
• Visible Light
– Frequencies detected by the nerves in the eyes ;
blue—shortest wavelength; red—longest
wavelength
• X-rays
– Can travel through matter and
produce images
– Dense parts of the body
absorb more than the soft
parts of the body
– Medical diagnosis
• Gamma rays
– Highest frequency, lowest
wavelength
– Medical treatments to kill
diseased cells, but also
damages healthy cells
Light waves
• a ray of light passes from one medium to
another, it bends
• Depending of the new medium the light will
travel faster or slower.
• the medium in which the light travels slower
( in this case the first one) is called the denser
medium.
Rarer medium and Denser
medium
• When a ray of light
enters a denser
medium, it is bent
towards the normal.
• When a ray of light
enters a rarer
medium, it is bent
away from the
normal.
Light Waves
• When a ray of light strikes a
plane mirror, the light ray
reflects off the mirror.
• Reflection involves a change in
direction of the light ray
Incident, Reflection and Normal
• incident ray -the ray of light
approaching the mirror
• reflected ray -The ray of light which
leaves the mirror
• normal line -At the point of
incidence where the ray strikes the
mirror, a line can be drawn
perpendicular to the surface of the
mirror;
The angle of incidence
•
is the angle between this normal
and the incident ray
The angle of reflection
• is the angle between this normal and the
reflected ray.
The Laws of reflection:
• - The angle of incidence is equal to
the angle of reflection
• - The incident ray, the normal, and
the reflected ray are coplanar
(lying or acting in the same plane )
Three types of materials that
affect light differently.
• Opaque- Block the light
• Translucent-May allow some light to
pass Ex: Stained glass.
• Transparent-allow the light to pass