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Mechanical Waves
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physical medium
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What can visible light be used for in communication?
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photography
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Transverse
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-pieces of medium vibrate perpindicular to direction of wave travel
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Wavelength
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Distance between *consecutive* points on a wave
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Electro Magnetic Waves
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medium --> space itself
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Retina
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The back surface of the eye.
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Ultrasonic
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Sounds with frequencies that are higher than 20,000HZ.
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Destructive Interference
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Decreases amplitude when waves interact.
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Two forms of wave?
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Electromagnetic and Magnetic
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Wave
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A method of transferring energy without transferring matter
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Transverse Waves
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PARTICLES VIBRATE PERPENDICULAR TO THE DIRECTION OF PROPAGATION
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Displacement,
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DISTANCE A PARTICLE IN A PARTICULAR MEDIUM IS FROM ITS EQUILIBRIUM POSITION (x)
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What is a Pulse?
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A single wave bump.
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what is the wave equation?
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wavespeed(m/s)= frequency(Hz)x wavelength(m)
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Transparent
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Matter through which visible light is easily transmitted.
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Infrasonic
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Sounds with frequencies that are lower than 20HZ.
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Real Image
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An image through which light passes.
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Amplitude
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Maximum displacement of a particle on the wave.
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convection
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the transfer of heat by the circulation or movement of the heated parts of a liquid or gas.
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Crest
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An upward movement in a transverse wave
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What are electromagnetic waves?
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Electromagnetic waves don't use particle vibration to transfer their energy (in fact particles interrupt their progress through a material) and can therefore travel through a vacuum. e.g. light
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Refraction
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When wave enters a medium where wave speed is different, wave fronts and rays will change direction (rays are perpendicular to fronts)
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Node
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POINT ON A STANDING WAVE WITH NO AMPLITUDE (DISTANCE BETWEEN NODES = 1/2 WAVELENGTH)
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Phase Difference
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THE AMOUNT BY WHICH TWO OSCILLATING PARTICLES OR WAVES ARE OUT OF STEP. (PHI)
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what does Opaque mean?
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does not let light thought
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Frequency
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The number of waves produced in a given amount of time.
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Interference
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The result of two or more waves overlapping.
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Wave Speed
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The speed at which a wave travels.
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Two types of wave movement?
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Longitudinal <--> Transverse (Up'n'Down)
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Phase
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Position of a particle in terms of Degrees or Radians, like a clock face from the axis.
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Totally Destructive Interference
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A special type of destructive interference where the waves cancel each other out totally and the resulting wave looks like equilibrium
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Nromal Line
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A line drawn perpendicularly to a serface
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What are mechanical waves?
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Mechanical waves use particles to transfer energy (neighbouring particles bump into each other and set their neighbours moving). Eg. sound waves use air particles so it cannot travel through a vacuum (a vacuum is empty space with no particles in it at all!). Sound travels faster through solids than liquids than gases because the particles are more closely packed.
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Law of Diffraction
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Waves bend around an obstacle, leaving a shadow region
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Spring force
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Fsp=-kx
The minus sign means it is a restoring force
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Damped Harmonic Motion (3)
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Harmonic motion with frictional force or drag
unwanted-clocks, pendulums
wanted-shock absorbers, earthquake protection
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Path Difference
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WAVES FROM TWO SOURCES MEET AT ONE POINT HAVING TRAVELLED DIFFERENT DISTANCES
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What type of wave has particles that move perpendicular to the motion of the wave?
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Transverse Waves
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What is superposition?
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When two waves overlap the resultant displacement is the algebraic sum of their seperate displacements.
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What are Waves?
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Transfering energy from one place to another
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Sonic Boom
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The explosive sound heard when a shock wave reaches your ears.
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Decibel (dB)
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The most common unit used to express loudness.
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Focal Length
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The distance between a mirror or lens through which all incident parallel light rays are focused.
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Diffuse Reflection
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The light beams will reflect at many different angles.
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Stationary Waves - Definition
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Have energy 'stored' between two points
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Equilibrium
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What a medium would look like if no wave were traveling through it
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Period
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The time it takes for one wave to pass
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Reflection
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The bouncing back of a wave after it encounters a new medium that does not absorb the wave's enegry
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Define a transverse wave.
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The vibrations in a transverse wave are perpendicular (at right angles) to the direction in which the energy is travelling. Eg. light.
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From LESS dense medium to MORE dense, which pulse (transmitted or reflected) is on the same side (in phase) as the incident phase?
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The transmitted pulse
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What is Frequency? (Hz)
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how many waves pass each second. measured in hertz
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Diffraction
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- the bending of light as it passes by an obstacle or through a barrier
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Concave Lens
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A lens that is thinner in the middle than at the edges.
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Standing Wave
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A wave fromed by two waves with the same amplitude and frequency traveling in the same meduim but in oppoisite directions
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What does a wave do?
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A wave transports energy from one place to another
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longitudinal waves (2) i.e.
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the motion of particles in the wave move parallel to it
i.e. sound waves, earthquakes
can move through liquid-in the transverse direction
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What two factors are the speed of waves dependent on?
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Tension and Mass/length (acceleration/speed increases when tension increases, mass decreases, and length of string decreases)
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Focal Point
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The point on the axis of a mirror or lens through which all incident parallel light rays are focused.
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In-Phase Points
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Any two points on a wave that are the same distance from equilibrium and are vibration in the same direction
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What is a Transverse wave?
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When vibration causes the wave to move perpendicular to the direction of energy transfer. and it moves in an up and down motion
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What is a Longitudinal Wave?
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When the vibration moves in the same diraction as the energy transfered.
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What can radio waves be used for in communication?
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tv, and radio
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Surface Wave
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In a body of water, is an example of a combination of both transverse and longitudinal waves.
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What is the velocity of a wave?
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The velocity at which the crests move.
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Do transverse waves need a substance to go through?
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Transverse waves do not need a substance to go through.
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What's special about electomagnetic waves, give an example.
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Need no medium, travel at C in a vacuum. e.g Light, Radio, Microwaves...
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Define a Longitudinal Wave. Give an example.
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The particles in the medium oscillate about their positions parallel to the direction of motion of the wave.
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From a MORE dense medium to LESS dense, how does the wavelength of the transmitted pulse compare to the reflected pulse?
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The transmitted pulse has a LARGER wavelength than the reflected pulse.
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Moving Source-Speed of the wave does not change, frequency and wavelength will change. When source moves towards the observer the frequency will increase, while wavelength will decrease. When source moves away from the observer the frequency will decrease
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Speed of the wave does not change, frequency and wavelength will change. When source moves towards the observer the frequency will increase, while wavelength will decrease. When source moves away from the observer the frequency will decrease, while wavelength will increase.
F1=f(v/v±vs), where F1= observed frequency, f= actual frequency, v= speed of the source,
vs=speed of the source. Moving away (+), moving towards (-)
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What's special about mechanical waves, give the main example.
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They need a medium to travel in, e.g Sound, Slinky Spring
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What happens when a wave reaches a boundary between two mediums? Does the frequency change?
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Part of the wave is transmitted and part of it is reflected. The frequency NEVER changes.
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What is the equation for working out the wave speed?
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Wave speed = frequency x wavelength
(metre / second, m/s) (hertz, Hz) (metre, m)
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