Download Chapter 16:Sound and Light

Principles of Earth and Physical Science
Mr. Taylor
Rainier Jr/Sr High School
 Sound
waves are caused by vibrations
and carry energy through a medium.
• Sound waves are longitudinal (push-pull) waves
 The
medium is the material that conducts
the energy from particle to particle.
• The speed of sound varies with the medium
• In general, more solid media conduct sound
faster.
 Loudness
is determined by intensity
(amplitude)
• Loudness is measured in decibels.
 Pitch
is determined by frequency
• High pitched sounds have high frequency
• Humans hear from about 20Hz to 20,000 Hz
• Lower than 20Hz = infrasound
• Higher than 20,000Hz = ultrasound
 Most
musical instruments produce sounds
by vibrating strings, membranes, or
columns of air.
• Instruments produce a fundamental frequency and
multiples of that frequency called harmonic
frequencies.
 Musical
instruments amplify these
frequencies by forcing vibrations of the
instrument body (resonance).
 The
ear uses resonance to vibrate nerve
endings.
• Vibrations are transmitted by the eardrum to the
inner ear where the nerve endings reside in the
cochlea.
 Distances
can be detected by measuring
the reflection of sound waves
• Ultrasound
• Sonar
 Light
can be modeled as
• a wave, or
• a particle.
 Light
as a wave follows the characteristics
we have been discussing:
• Reflection, refraction, diffraction, interference,
etc.
• Light acts as a transverse electromagnetic wave
 Light
can be modeled as
• a wave, or
• a particle.
 Light
as a particle is described as
“packets of energy called photons.
• A photon has energy related to its frequency:
 High frequency is high energy
 Low frequency is low energy
 The
speed of light varies with the medium:
• In a vacuum light travels at approximately 3x108
meters/second (186,000 miles/second)
 The
brightness of light varies with
intensity and is often measured in lumens.
 Light
is part of the electromagnetic
spectrum
 Light
is both absorbed and reflected
from any surface it hits.
 The Law of Reflection:
• The angle of incidence = the angle of reflection.
• The “normal” is a right angle to the surface.
 Mirrors
reflect light
• Flat mirrors create a virtual image. The image
looks like it is behind the mirror, but not light
rays are located there.
• Curved mirrors create a distorted image.
 Concave mirrors curve in
 Convex mirrors curve outward
 Convex mirrors can create a real image. This is how
light is focused from a projector onto a wall/screen.
 Colors
depend on the wavelength of light
striking the eye.
 The color of any object is a result of the
light they reflect or transmit.
 Transmitted light has 3 basic colors:
• Red
• Green
• Blue
 All
colors are a result of mixing these 3
colors of light
 Colors
depend on the wavelength of light
striking the eye.
 The color of any object is a result of the
light they reflect or transmit.
 Reflected light has 3 basic color pigments:
• Yellow
• Cyan
• Magenta
 All
colors are the result of mixing these 3
basic pigments.