waves physical science. what is a wave? movement of energy through a medium by vibrations
TRANSCRIPT
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WavesPhysical Science
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What is a Wave?
• Movement of energy through a medium by vibrations
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Mediums are what?
• Materials that waves transfer though
• Types
–Liquids
–Air/gases
–Solid best for sound waves
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What moves in a Wave?
• Energy–A wave will
move as along as it has energy to carry
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Types of Waves
A. Mechanical Waves– Is a disturbance in
matter that carries energy from one place to another
– Ex: sound waves
B. Surface Waves– Is a wave that travels
along a surface separating two mediums
– Ex: ocean waves (water and air)
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Types of Waves
C. Electromagnetic Waves–Transverse waves consisting
of changing electric fields & changing magnetic fields
–Ex: x-rays, radio waves
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Types of Mechanical Waves
A. Transverse Waves– Is a wave that causes a
medium to vibrate at right angles to the direction of travel
–Up and Down motion
–Ex: Light waves
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Types of Mechanical Waves
B. Longitudinal Waves– Is a wave in which the
vibration of the medium is parallel to the direction of travel.
– Back and forth motion
– AKA: compressional waves
– Ex: Sound Waves
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Wave Parts—Transverse Waves only
• Crest—highest point on a wave (top of wave)
• Trough—lowest point on a wave (bottom of wave)
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Wave Parts—Longitudinal Waves Only
• Compression—area where particles are close together
• Rarefaction—area where particles are spread out
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Wave PartsTransverse & Longitudinal Waves
• Wavelength– Distance between a
point on one wave to the same point on the next wave
– Transverse Waves• Crest to crest
• Trough to trough
– Longitudinal Waves• Compression to
compression
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Wave PartsTransverse & Longitudinal Waves
• Amplitude–Max displacement of
the medium from resting position
– Transverse Wave• Resting position to
crest/trough
– Longitudinal Wave• How compressed the
compressions are
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Transverse Wave Diagram
A. Crest
B. Trough
C. Wavelength
D. Amplitude
E. Wave Height
F. Resting Position
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Longitudinal Wave Diagram
A. Compression
B. Rarefaction
C. Wavelength
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Frequency of a Wave
• Amount of waves that pass a given point in one second
• Unit= Hertz (Hz)
• Transverse waves– Count the top and
bottom pairs
• Longitudinal waves– Count the compressions
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Frequency Practice
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Frequency & Energy Relationship
• As frequency increases, the energy in a wave increases
• They do the same
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Frequency & Wavelength Relationship
• Increase frequency decrease the wavelength of a wave
• They do the opposite
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Wavelength & Energy Relationship
• Increase the wavelength will decrease the energy
• They do the opposite
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Amplitude & Energy Relationship
• As the energy of a wave increases, the amplitude increase
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Frequency & Period Relationship
• What is Period?– The amount of time it
takes one wavelength to pass a point
• Relationship– As the frequency of a
wave increase, the period decreases.
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Wave Speed Formula
• Wave Speed = frequency * wavelength
Vw = f * λ
• Vw= wavespeed (m/s)
• f = frequency (Hz)
• λ = wavelength (m)
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Wave Speed Example Problems
1. A wave has a wavelength of 4 meters and a frequency of 20 Hz. What is the speed of the wave?
2. A wave has a speed of 10 m/s and a length between the crests of 0.5 meters. What is the frequency of the wave?
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Speed of Light and Sound
• Light Waves = 3 x 108 m/s
• Sound waves = 340 m/s
• Light travels faster than sound
• This is why you see lighting before hearing thunder
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Electromagnetic Waves
• Placed in the electromagnetic spectrum
• Arranged by wavelength and frequency
• Can travel through a vacuum
• Likes no medium
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Electromagnetic Spectrum
• AKA: E-M spectrum
• Moving from left to Right–Wavelength Decrease
– Frequency Increases
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Types of Electromagnetic Waves
A. Radio Waves– Longest Wavelength
– Lowest frequency
– Types: radio, TV, microwaves, radar
B. Infrared Rays– Can’t see with out
eyes
– Used to Detect Heat
– Ex: heat lamps, night vision goggles
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Types of Electromagnetic Waves
C. Visible Light–We Can See
–White Light can be broken down• ROY G BIV
– Red Light• Longest wavelength
• Lowest frequency
– Violet Light• Shortest wavelength
• Highest frequency
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Types of Electromagnetic Waves
D. Ultraviolet Rays– Body uses to make
vitamin D
– Causes sunburns
– Can cause skin cancer
–We can’t see
E. X-Rays– Can pass through skin
– Cannot go through bones
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Types of Electromagnetic Waves
F. Gamma Rays– Highest Frequency
on E-M spectrum
– Highest energy on E-M spectrum
– Found in Space
– Stopped by 3-m of lead
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Wave Interactions
• How waves behave when they met a surface, barrier, or another wave
• Four Basic Types– Reflection
– Refraction
– Diffraction
– Interference
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Reflection
• Waves bounce off or back
• Speed and Frequency does not change
• Two Types– Regular
– Diffuse
• Ex: Sonar, Radar
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Types of Reflections
• Regular– All waves bounce off
a surface at the same angle
– Image is clear
• Diffuse–Waves scatter off a
bumpy surface
– Image is hard to see
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Refraction• Bending of a wave as it
enters a new medium at an angle
• Direction never changes but wavelength and speed does
• Ex: – waves coming inshore
– pencil in cup of water
– Light entering glass
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Diffraction• Bending of a wave as it
moves around an obstacle or passes through a narrow opening
• Ex:
– Ocean waves with a barrier
–Why you hear a parade around a corner
– Causes light to scatter (reason the sky is blue)
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Interference
• Occurs when two waves overlap and combine together
• Two Types– Constructive
– Destructive
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Constructive Interference
• When two waves moving in the same direction collide and produce a wave with a larger displacement
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Destructive Interference
• When 2 waves moving in opposite directions, collide and produce a wave with a smaller displacement