P5 Flashcards
What are waves
An oscillation that transfers energy
What are longitudinal waves
Waves that have oscillations parallel to energy transfer
They require a medium like air as the energy is transferred when particles collide
When the oscillations are further apart there are rarefractions
When they are close together there are compressions
What are transverse waves
Waves that move (oscillate) at 90° to the direction of energy transfer
They do not always require a medium to travel through
What is amplitude
Distance from the trough to the crest of a wave (bottom to top)
Symbol - A
Measurement - depends on the wave, e.g m or v
What is wavelength
The distance from one point of a wave to the same point on the next eave
Symbol - λ - lambda
Unit - meters
What is frequency (waves)
The number of oscillations per second
Symbol - F
Units - Hertz
What is the time period (waves)
The time taken for a wave to pass a specific point
Symbol - T
Unit - seconds
What is wave velocity
The speed at which a wave transfers energy or information
How do you calculate wave velocity
Frequency × wavelength
How can waves be modeled
Using a ripples on water to model transverse waves
What happens when waves enter a different medium
Their velocity change causing the wave to refract
Why does entering a denser medium cause a wave to refract
Entering a denser medium causes the speed of the wave to decrease
So waves bend towards the normal
The wave length decreases and the frequency stays the same
What happens to sound waves at a boundary
They are either
Absorbed
Transmitted
Reflected
What is an echo
A refraction of sound
What is echo sounding
A process of finding the distance between two points, by using the time it takes to reflect a sound wave
What is sonar
Sound
Navigation
And
Ranging
It is used to find distances using echo-sounding
What is ultrasound
A sound frequency greater than 20,000hz
We cannot hear it but many animals can
Why is ultrasound usefull
It has a short wavelength so can easily be focused into a beam
How is ultrasound used
It can be used to make an image of a fetus
Ultrasound beams are transmitted into the mother (by the transmitter)
As there are different boundaries the waves are reflected and absorbed
The machine calculates the distance of each point using time and velocity, and those points are used to create an image
(Distance is divided by 2)
It is also used in sonar and echo-sounding
What happens when a sound wave hits a solid
After being reflected many times some of the sound is absorbed, making objects in the particle vibrate and heat up
How does your ear detect sound
The outer ear gathers the sound wave and directs it to the ear drum which vibrates
The ear drum makes the ossicles vibrate which amplify the vibration, passing it on to the inner ear.
The Cochlea then transmits these movements of the oval window to small hairs through a liquid.
These hairs (cillia) are attached to sound-detecting cells which release a chemical that causes a nerve to travel to the brain (auditory nerve)
Your brain then turns this into sounf
Why can we only hear certain frequencies
Hairs on your cochlea have a natural frequency
They have different lengths and resonate with different frequencies
The range of sound you can hear depends on the size of the hairs
The smaller the hairs the lower the frequency
Why do we stop being able to hear high frequency sounds as we get older
The short hairs that detect high frequencies fall out
What are electromagnetic waves
Transverse waves caused by oscillating electric and magnetic fields
They do not require matter - they all travel through a vacuum