SP4 Waves Flashcards
(30 cards)
Define transverse waves
The vibrations are perpendicular to the direction to travel
Define longitudinal waves
The vibrations are parallel to the direction of travel
Examples of transverse waves
EM waves, S-waves, ripples/waves in water
Examples of longitudinal waves
Sound waves, P-waves
Describing waves
The amplitude is…
the displacement from the rest position to a peak or trough
Describing waves
The period is…
the number of seconds it takes for one full cycle
Period = 1 / frequency
Formula for wave speed
Wave speed = frequency x wavelength
OR
Wave speed = distance / time
How do you measure velocity of sound in air?
By attaching a signal generator to a speaker, you can generate sounds with a specific frequency. Use two microphones and an oscilloscope to find the wavelength of the sound waves generated
How do you measure the velocity waves on the surface if water?
Using a signal generator attached to the dipper of a ripple tank, you can create water waves at a set frequency. Then dim the lights and use a strobe light to see a wave pattern. Alter frequency of strobe light until wave pattern seems to “freeze”. The distance between each shadow line is equal to one wavelength. Measure distance between lines that are 10 wavelengths apart and find average
What is refraction?
The change in direction of a wave at a boundary
What happens when a wave travels along the normal?
It will change speed as it crosses a boundary, but it will not change direction (refraction)
What happens when a wave hits the boundary at an angle?
The change of speed causes a change in direction because of the angle it has hit the boundary. This causes refraction
Define specular reflection
Occurs when waves are reflected in a single direction by a smooth surface
Define diffuse reflection
Occurs when waves are reflected by a rough surface and the waves are reflected in all directions
What is reflection?
Where the incoming ray is neither absorbed nor transmitted, but instead is ‘sent back’ away from the second material - this is how echoes are created
List the order in which the ear transmits vibrations
Eardrum, ossicles, semicircular canals, cochlea, auditory nerve
What does your outer ear do?
Sound waves reach your ear drum and cause it to vibrate.
What does your middle ear do?
Vibrations from drum are passed to tiny bones called ossicles, through the semicircular canals and t the cochlea
What does your inner ear do?
The cochlea turns these vibrations into electrical signals which gets sent to your brain, that then interprets the signal as sounds of different pitches and volumes
Limitations to human hearing
1) shape of eardrum
2) size of eardrum
3) structure of parts within ear that vibrate
Why can human ear only detect a certain range of frequencies?
Depends on the range of lengths of hairs in the cochlea. As a person ages, the shorter hairs that respond to higher frequencies stop working
A pulse of ultrasound takes 4.5 secs to travel from submarine to seabed and back again. If speed of sound in seawater is 1520 m/s, how far away is the submarine from the seabed?
4.55 / 2 = 2.25 secs there
1520 x 2.25 = 3420m away
What is ultrasound?
Frequencies greater than 20,000 Hz
How is ultrasound used in sonar?
In echo sounding, which is used by boats and submarines to find out the distance of the seabed / locate objects deep in water
