a wave is a disturbance that transmits energy through matter or space
TRANSCRIPT
A wave is a disturbance that transmits energy through matter or space.
A mechanical wave must
have a medium to be able to travel.
Electromagnetic waves consist of alternating
electric and magnetic fields in space and do not
require a medium to travel.
Most waves travel through a medium
A medium is the matter or “stuff” through
which a wave travelsFor example: Water, air,
the ground, rock, etc.
Electromagnetic waves DO NOT
require a medium, and actually
travel best when in a vacuum.
Light waves consist of changing electric and magnetic fields in space which are
called electromagnetic
waves.
EXAMPLES OF ELECTROMAGNETIC
WAVESRadio WavesTelevision WavesVisible LightX-raysUV Rays
Waves transfer energy
Does a wave travel on forever?
NOEnergy may
spread out as a wave travels
Waves are related to vibrations
Waves are caused by vibrating objects.
Particles in a medium can either vibrate
1) perpendicularly2) parallelto the direction of
wave motion
Transverse Waves The particles of
the medium vibrate perpendicularly to the direction the wave travels. EXAMPLES:
Stadium wave, light wave
Longitudinal Waves The particles of the
medium vibrate parallel to the direction the wave travels.
EXAMPLES: Sound Waves
In a surface wave, particles move in a circle. (perpendicularly and parallel
Surface waves occur at the boundary of two mediums
For a sine or transverse wave:Crests – high pointsTroughs – low pointsAmplitude – distance from the midpoint to the crest
(or from the midpoint to the trough)Wavelength – distance between 2 consecutive pts.
of a wave (nm)Frequency - how often a vibration occurs (Hz)
Frequency determines the pitch of the sound
Amplitude determines how loud or soft a sound seems to be.
Frequency – The number of wavelengths that
pass a fixed point each second.
Measured in Hertz (Hz)
For example: 20 vibrations/second is the
same as 20 Hz.
150 Hz is the same as 150 vibrations/second.
The wave period is the amount of time it takes
for a wavelength to pass a point.
As the frequency of a wave increases, the wave period decreases.
Periods are measured in units of seconds.
The speed of a wave depends on the medium it is traveling through.
It can be calculated using the following equation:
Speed (in m/s) = frequency (in Hz) x wavelength (in m)
ORv = f x λ
Waves can experience four types of interactions
1) Reflection2) Diffraction3) Refraction4) Interference
Reflection The bouncing back
of a wave as it meets a boundary.
Waves reflect at a free boundary
When a wave hits a fixed boundary, it is reflected and turned upside down to travel back in the opposite direction
Diffraction - Bending of a wave as it passes an edge or an opening.
**Stays in the same medium
Refraction The bending of waves as they pass from one medium to another.
**Change mediums.
Example, fish underwater, or looking at fish in an aquarium.
INTERFERENCE This occurs when several waves are in the same location and combine to produce a single, new wave that is different from the original wave.
Interference of Sound waves creates beats in the music
Wave Interference – When 2 or more waves interact, it results in interference.
Interference can be:1) Constructive2) Destructive
Constructive Interference When the crest of one wave overlaps the crest of another wave, they reinforce each other, and create a wave with an added amplitude.
Amplitudes are added.
Destructive Interference When the crest of one
wave meets the trough of another wave; they detract from each other, and create a wave with decreased amplitude.
Amplitudes are subtracted.
Standing Waves Wave form that appears to not move
along the medium Creates regions of no vibration
(nodes) (Complete destructive interference)
Creates regions of maximum vibration (antinodes) (Complete constructive interference)