What are
waves?
Wave
Definition: A disturbance that transfers
energy from place to place.
What carries waves? A medium, a
medium is the material through which a
wave travels.
A medium can be a gas, liquid, or solid.
What causes waves?
Waves are created
when a source of
energy causes a
medium to vibrate.
A vibration is a
repeated back and
forth or up and
down motion.
Types of waves: Waves are
classified according to how
they move.
Transverse wave
Waves that move the
medium at right angles
to the direction in which
the waves are traveling
is called a transverse
wave.
Transverse means
across.The highest
parts are called crests
the lowest parts are
called troughs.
Longitudinal Wave
Matter vibrates in
the same direction
as the wave travels.
Example: Slinky
Longitudinal wave
The parts,where the
coils are close
together are called
compressions, the
parts where the coils
are spread out are
called rarefactions.
Properties of Waves
Basic Properties of Waves
Amplitude
Wavelength
Frequency
Speed
Draw Transverse wave and
label: crest & trough
the old Slinky song)
Amplitude of transverse waves
The amplitude of a transverse wave is
the maximum distance the medium
moves up or down from its rest
position. You can find the amplitude of
a transverse wave by measuring the
distance from rest position to crest or
rest position to trough.
The greater the amplitude the greater
the greater the energy the wave has.
Wavelength of Transverse
wave
The distance between crest to crest or
trough to trough.
Amplitude of a longitudinal
wave.
The amplitude of a longitudinal wave is
a measure of how compressed or
rarefied the medium becomes.
Frequency
The number of complete waves that
pass a given point in a certain amount
of time.
Frequency measured in hertz (Hz).
The shorter the wavelength the higher
the frequency
Frequency and energy: The higher the
frequency the more energy the wave
has.
Speed
The speed, wavelength, and frequency
of a wave are related to each other by a
mathematical formula.
Speed = wavelength x frequency
Frequency = speed/wavelength
Wavelength = speed/frequency
Speed
Waves in different
mediums travel at
different speeds.
However, in a given
medium and under
the same conditions
the speed of the
wave is constant.
Ways Waves Interact
Reflection
Refraction
Diffraction
Interference
Constructive
Destructive
Absorption and
scattering
Reflection
When an object or wave hits a surface
through which it cannot pass, it bounces
back.
Angle of incidence: The angle made by the
beam of light traveling toward the mirror
Angle of reflection: The angle made by the
beam of light reflecting from the mirror.
Law of reflection
The angle of incidence=the angle of
reflection
Examples of reflection
Mirror
Echo
Ball against a wall
Refraction is when a wave moves
from one medium into another
medium at an angle, it changes
speed as it enters the second
medium which causes it to bend.
The bending of waves due to a
change in speed is called
refraction.
Refraction
Diffraction
When a wave passes a barrier or moves
through a hole in a barrier it bends and
spreads out.
Interference
Constructive interference occurs
whenever two waves combine to make
a wave with a larger amplitude.
Destructive interference
when the amplitudes of two waves combine
producing a smaller amplitude.
Absorption
Some of the light energy
gets absorbed before it is reflected back
Example: when you shine a flash light in the
air, the air particles absorb some of the
energy from the light and that caused the
light to become dim
Scattering of light
It is like the scattering of light beam
when it comes out of the sun
Not all waves require a
medium to travel.
Light from the sun travels through
empty space.
Mirrors
Plane mirror: your
picture in the mirror
is reversed.
Lenses
Convex lense
Convex lense
Longitudinal waves
Draw a Compressional wave:
label compression& rarefaction
Resonance
Most objects have a natural frequency of
vibration. Resonance occurs when vibrations
traveling through an object match the object’s
natural frequency.
An object that is vibrating at its natural frequency
absorbs energy from the objects that vibrate at
the same frequency. Occurs in music.