Waves for communications and the universe Flashcards
Waves transfer what?
Energy.
Waves can either be what type?
Transverse or longitudinal.
EM waves are what type of waves?
Transverse.
Sound waves are an example of what type of waves?
Longitudinal.
EM stands for…
…the electromagnetic spectrum.
Longitudinal waves show areas of what and what?
Compression and rarefaction.
Waves can be reflected,…
…refracted and diffracted.
Waves under go what when they are refracted at an interface?
A change in direction.
All waves obey the wave equation with the formula:
v = f x lambda
v = velocity in m/s f = frequency in Hz lambda = wavelength in m
What waves of the EM spectrum can be used for communications?
Radio waves (TV and radio), microwaves (phone signal), infrared (remote controls) and visible light (photography).
What is the normal?
A construction line perpendicular to the reflecting surface at the point of incidence.
The angle of incidence is equal to…
…the angle of reflection.
The image produced by a plain mirror is a…
…virtual image.
Sound waves are longitudinal and cause…
…vibrations within a medium.
Pitch of sound is determined by what?
Its frequency.
Loudness of sound is determined by what?
Its amplitude.
An echo is a what of sound?
Reflection.
If a wave source is moving relative to the observer what happens?
There is a change in the observed wavelength. This is known as the Doppler Effect.
There is an increase in wavelengths of light from the most distant galaxies. Why is this?
The further away a galaxy is the faster that it is moving away and the bigger the observed increase in wavelength. This is known as red-shift as the wavelength is increasing towards the red end of the spectrum.
The observed red-shift provides evidence for what theory of the beginning of the universe?
Evidence for the Big Bang. This is because if we reverse the effect of red-shift with time the universe contracts to form an infinitely small, infinitely dense singularity from which everything must have occurred.
What is CMBR and what does it stand for?
Cosmic Microwave Background Radiation. It is radiation that fills the universe and was present shortly after the beginning of the universe.
What theory of the beginning of the universe is the only theory that can explain CMBR?
The Big Bang.
