physics topic 6 Flashcards
(69 cards)
describe transverse waves
Vibrations are perpendicular to the direction of energy transfer.
Electromagnetic waves travel at what speed
at the speed of light
(3x10^8m/s)
give examples of transverse waves
Water waves,
electromagnetic (light) waves
describe Longitudinal waves:
Vibrations are parallel to the direction of energy transfer.
what are some examples of longitudinal waves
Sound waves and a type of seismic (P) wave.
what is wavelength (λ)
distance from one point on a wave to the same
point on the next wave.
what is Amplitude (m)
maximum displacement from its undisturbed position.
what is Frequency (Hz)
waves per second.
what is Period (s)
the time taken to produce one complete wave.
give the practical for measuring the speed of sound in air
- Student A hit two cymbals together and student B started a stopwatch.
- When student A heard an echo she hit the cymbals together again.
- Student B stopped the stopwatch after timing 5 echoes.
- Calculate an average time for the echoes and ÷ by 2 (there and
back) - Use a measuring tape to work out the distance between students and wall
- Speed = Distance / Time
why does sound move faster through solids
- Sound needs particles to travel
- In a solid, particles are very close together
- So sound is fastest through a solid
describe the Ripple tank practical (investigating waves)
Frequency
* use a stopwatch
- count the number of waves passing a point in 10 seconds
- Number of waves / 10 seconds = average frequency
Wavelength
- use a camera to freeze the image
- use a metre rule to measure the distance between 10 waves
- divide distance by 10 to determine average λ
Velocity
* use v=fλ
what happens when a sound wave travels from one medium to another e.g. air to water
the frequency remains the same.
The sound wave will travel faster in water than air.
what happens if if the frequency remains the same, as velocity increases
wavelength must also increase proportionally.
what is the Human hearing range
20Hz and 20,000Hz (20kHz). Anything above this is
called ultrasound
what is anything’s above 20,000Hz called
ultrasound
describe how Ultrasound waves are used for detection
Ultrasound waves are partially reflected
when they meet a boundary between
two different media.
The time taken for the reflections to meet
a detector can be used to determine how
far away the boundary is.
describe some medical uses for ultrasound
- Pre-natal scanning
- Imaging (a named body part).
why is ultrasound safe to use
Ultrasound does not damage (human) cells
describe Echo
location/SONAR
Echo location or SONAR uses high frequency sound waves to detect objects in deep water and measure water depth
what waves do earthquakes produce
Earthquakes produce P and S waves.
describe P waves
fast longitudinal; travel at different speeds through solids and liquids.
describe S waves
slower transverse; cannot travel
through liquids.
what can p waves and s waves lead us to understand about the earth
This information can be used to determine the size, density and state of the Earth’s structure. As S waves do not penetrate the outer core, they can not be used to determine whether the inner core is liquid or solid.