3 Waves Flashcards
what is hertz measuring
the frequency of something
what is the frequency of a wave
the amount of cycles per second
the pitch
longitudinal waves
the waves oscillate in the parallel (same direction) to the direction they travel in
transverse waves
the waves oscillate perpendicular (at right angles) to the direction they travel in
examples of longitudinal waves
sound waves
seismic p-waves
spring/slinkie
examples of transverse waves
electromagnetic waves
ripples in the sea
mexican wave
seismic s-waves
rope
what is the amplitude of a wave
The distance from the undisturbed position to the peak or trough of a wave
the volume
what is the wavefront of a wave
the wavefront is a way of drawing a wave from above (all of the waves are drawn in the same phase, eg all troughs)
each line represents one wave and if they are close together that shows a high frequency
what is the wavelength of a wave
The distance from one point on the wave to the same point on the next wave
what is the period of a wave
the time it takes for one wavelength to happen
what do waves transfer
transfer energy and information, without transferring matter
what is the formula with wavelength, frequency, wave speed
wave speed = frequency x wavelength
v=fλ
what is the formula with frequency and time period
frequency = 1 / time period
f=1/T
what is the doppler effect
the change in wavelength and frequency of a wave emitted by a moveing source
why does the doppler effect change the frequency of a wave
When the source of the wave is moving towards the observer, each successive wave cycle is emitted from a position closer to the observer than the previous cycle. As a result, the time between the arrival of each wave at the observer is reduced, which effectively increases the frequency of the wave as observed by the observer2.
Conversely, if the source of the wave is moving away from the observer, each wave cycle is emitted from a position farther from the observer than the previous cycle. This increases the time between the arrival of each wave at the observer, effectively reducing the observed frequency
why does the doppler effect change the wavelength of a wave
When the source of the wave is moving towards the observer, each successive wave cycle is emitted from a position closer to the observer than the previous cycle1. This causes the wavefronts to “bunch up”, effectively shortening the wavelength as observed by the observer3. This is why waves appear “squeezed” or “compressed” when the source is moving towards the observer4.
Conversely, if the source of the wave is moving away from the observer, each wave cycle is emitted from a position farther from the observer than the previous cycle1. This causes the wavefronts to spread out, effectively lengthening the wavelength as observed by the observer3. This is why waves appear “stretched out” when the source is moving away from the observer
can all waves be reflected or refracted
yes in the right circumstances
what type of wave is light waves
transverse
can light waves be reflected or refracted
yes
what is the law of reflection
The law of reflection states that the angle of incidence (the angle at which the wave hits the surface) equals the angle of reflection (the angle at which the wave bounces off the surface).
what is reflection
A wave hits a boundary between two media and does not pass through, but instead stays in the original medium
where angle i = r
what is the formula with refractive index, angle of incidence, angle of refraction
refractive index = sin(angle of incidence) / sin(angle of refraction)
n = sin(i) / sin(r)
practical: To investigate the refraction of light using rectangular blocks, semi-circular blocks and triangular prisms
Place the block on a sheet of paper, and carefully draw around the rectangular perspex block using a pencil
Switch on the ray box and direct a beam of light at the side face of the block
Mark on the paper:
- A point on the ray close to the ray box
- The point where the ray enters the block
- The point where the ray exits the block
- A point on the exit light ray which is a distance of about 5 cm away from the block
Draw a dashed line normal (at right angles) to the outline of the block where the points are
Remove the block and join the points marked with three straight lines
Replace the block within its outline and repeat the above process for a ray striking the block at a different angle
Repeat the procedure for each shape of perspex block (prism and semi-circular)
practical: investigate the refractive index of glass using a glass block
Place the glass block on a sheet of paper, and carefully draw around the rectangular perspex block using a pencil
Switch on the ray box and direct a beam of light at the side face of the block
Mark on the paper:
- A point on the ray close to the ray box
- The point where the ray enters the block
- The point where the ray exits the block
- A point on the exit light ray which is a distance of about 5 cm away from the block
Draw a dashed line normal (at right angles) to the outline of the block where the points are
Remove the block and join the points marked with three straight lines
Replace the block within its outline and repeat the above process for a ray striking the block at a different angle
measure the angle of incidence and angle of refraction and then use n = sin(i) / sin(r)