1.2 Listening to Sounds Flashcards
What is amplitude?
The amplitude is the maximum displacement from its rest position of one of the particles to the medium that carries the wave.
What are light waves?
Unlike sound, a mechanical wave, light does not need a substance to travel through. Most substances easily absorb light. Light slows down when travelling through transparent substances. Light travels in an electromagnet wave. This is a varying electric field and magnetic field which are at right angles to each other and to the direction of travel of the wave.
What kind of a wave is light?
Transverse- where the energy travels in a direction at right angles to the direction of vibration.
What is the speed of light?
3.00 x 10^8 m s ^-1. A factor of about a million times faster than sound.
What do sound and light waves have in common?
They reflect, refract, diffract and superpose.
What is polarisation?
Polarisation effects transverse waves but not longitudinal waves. Polarisation of a transverse wave restricts the oscillation so that it only occurs in one plane perpendicular to the direction of travel.
Why can longitudinal waves not be polarised?
This is because sound waves travel in the same direction as the oscillation of the particles they travel through.
How do you measure the speed of sound?
Two microphones connected to a fast timer.
Hammer strikes a metal plate= pulse of sound.
Nearer microphone picks this up first.
Followed by the second microphone when the pulse of sound has travelled an extra meter.
The sound pulse causes the microphones each to generate an electrical pulse.
The pulses trigger the timer to start and stop.
The speed of sound is simply the extra distance travelled by the sound pulse (1.0m) divided by the time.
The speed of a wave travelling across a water surface is greater for waves of longer wavelength. If the speed of a sound wave was also dependent on wavelength, what effect would this have when listening to an orchestra?
Sound waves of different frequency would travel at different speeds.
Sounds of different frequencies generated at the same time would therefore reach the listener at different times.
Musical notes produced by an instrument would sound very different as you moved away from them.
Explain why it is important that members of an orchestra watch the conductor weather than just listen to the music from other instruments?
If just listen then you are relying on sound
waves.
Time taken for sound waves to reach different members of the orchestra would
differ as the sound waves travel different distances.
Light waves travel very quickly and so members of the orchestra will see the
movement of the conductor at the same
time.
Describe how the normal human ear has a sensitivity that varies with frequency?
Sensitive from 20 Hz to 20 kHz.
Most sensitive between 2 kHz and 4 kHz.
As ear amplifies frequencies in this range more.
