Topic 6 - Waves Fundamentals Flashcards
What is a wave?
An oscillation that transfers energy without transferring any matter, it makes the particles of the substance that it’s travelling through oscillate
Define a transverse wave
They oscillate at 90 degrees (perpendicular) to the direction of energy transfer of the wave (the direction that they travel in)
Define a longitudinal wave
The oscillations are parallel to the direction of energy transfer of the wave (the direction they travel)
What is an area of rarefaction in LW?
Where the particles are spread out
What is an area of compression in LW?
Where the particles are bunched together
Give 3 examples of transverse waves
• light waves (all EM waves)
• ripples on the surface of water
• seismic S-waves
Give 3 examples of longitudinal waves
• sound waves
• ultrasound waves
• seismic P-waves
What are the two axis labeled on a wave diagram? (TW)
Y= displacement
X= distance or time (also the rest position)
Name and define the parts of a wave diagram (TW)
Peaks - maximum positive displacement
Troughs - maximum negative displacement
What is amplitude? (TW)
The amplitude is the maximum displacement of a point on the wave from its undisturbed (rest) position
What is wavelength?
The distance between the same point on two adjacent waves (on longitudinal waves it is the distance between two centres of two adjacent compressions)
What is frequency?
It is the number of complete waves passing a certain point per second, it is measured in hertz (Hz)
What is the equation for frequency?
Frequency = 1/period
What is the period of a wave?
The amount of time it takes for a full cycle of the wave to be completed
Define wave speed
The speed at which energy is being transferred (the speed the wave is moving at)
What is the equation for wave speed
Wave speed = wavelength x frequency
what is absorption of a wave at a boundary
the waves may be absorbed by the material the wave is trying to cross into. this transfers energy to the materials energy store.
what is reflection of a wave at a boundary
the waves may bounce back
what is transmission of a wave at a boundary
the waves may be transmitted, this means that they carry on travelling through the new material. however, they often undergo refraction.
explain refraction
if a ray hits the boundary at an angle, it changes direction. refraction occurs because waves travel faster in some materials than others, so the speed can change as it crosses the boundary. its speed changes but the frequency stays the same. wavelength also changes.
what is optical density
measure of how quickly light travels through a material - the higher the optical density, the slower the light travels.
What are wavefronts
They are imaginary line drawn through certain points on waves e.g. through the peak, they’re perpendicular to the direction in which the wave is moving
Why does a wave change direction
When a wave crosses a boundary into a new substance at an angle to the normal, one end of it enters the new material before the rest of the wave. This means that end changes speed before the rest of the wave, causing the wave to change direction.
