Download LIGHT: What is it?

NATURE OF WAVES
© 2000 Microsoft Clip Gallery

Waves (Def.) – A wave is a disturbance that
transfers energy.

Medium – Substance or region through
which a wave is transmitted.

Speed of Waves – Depends on the
properties of the medium.
LIGHT: What Is It?
© 2000 Microsoft Clip Gallery
Video
Light Energy
 Atoms
As atoms absorb energy, electrons jump
out to a higher energy level.
Electrons release light when falling
down to the lower energy level.
 Photons - bundles/packets of energy
released when the electrons fall.
 Light: Stream of Photons

© 2000 Microsoft Clip Gallery
Electromagnetic Waves
 Speed
in Vacuum
 300,000 km/sec
 186,000 mi/sec
 Speed in Other Materials
 Slower in Air, Water, Glass
 Speed of Light Video
© 2000 Microsoft Clip Gallery
Transverse Waves
© 2000 Microsoft Clip Gallery
 Energy
is perpendicular to direction of
motion
 Moving photon creates electric &
magnetic field
 Light has BOTH Electric & Magnetic
fields at right angles!
Electromagnetic Spectrum
© 2000 Microsoft Clip Gallery
Electromagnetic Spectrum
Spectrum – Light we can see
 Roy G. Biv – Acronym for Red,
Orange, Yellow, Green, Blue, Indigo, &
Violet.
 Largest to Smallest Wavelength.
 Visible
Refraction of Light
Refraction – Bending of
light due to a change in speed.

Occurs when the wave enters a new medium.
 Index of Refraction – Amount by which a
material refracts light.
 Prisms – Glass that bends light. Different
frequencies are bent different amounts & light
is broken out into different colors.

Refraction (Cont.)
Video
Reflection of Light
 Reflection
– Bouncing back of light
waves
The Law of Reflection states that the angle of
incidence equals the angle of reflection
 Regular reflection –smooth surfaces scatter
light very little. Images are clear & exact.
Ex: mirrors
 Diffuse reflection – reflected light is
scattered due to an irregular surface. Ex:
walls

Video
Diffraction
 The
bending of waves
around a barrier or through
an opening.
New waves are formed from the
original
 Light waves diffract much less
than sound waves.

Wave Interference

Two waves combining to form a new
wave.
Constructive Interference

Occurs when waves combine to make a
wave with a bigger amplitude.
Occurs when the
crests overlap, they
make higher crests
 The new amplitude
is equal to the net of the
the amplitude of the two
crests that combine.

Destructive Interference

Occurs when the waves combine to make
a wave with a smaller amplitude.
Occurs when the
Crest of one wave overlaps
With the trough of another wave.
 If the crest has a larger amplitude than
the trough, the crest amplitude decreases
and part of it will remain.
 If the original waves had equal
amplitudes, then the crest and through
completely cancel each other out.
