Science physics revision Flashcards
What is a progressive wave
A wave that transfers energy from place to another without transferring material
What is amplitude
maximum displacement from rest position
What is wavelength
The distance between two matching points on neighbouring waves
What is frequency
The number of waves that pass in a certain amount of time
What is a transverse wave
The oscillations are perpendicular to the direction of wave travel
What is a longitudinal wave
The oscillations are parallel to the direction of wave travel
What is the equation to calculate wave speed
frequency times wavelength
What is a stationary wave
A wave that travels in opposite directions and this requires the same frequency but different constant phase
What is the phase difference of constructive difference
0
What is the phase difference of destructive interference
180
Describe bright spots
It has constructive interference, maximum amplitude and the peak meets with a peak and it has a phase difference of 0
Describe dark spots
It has destructive interference, minimum amplitude, the peak meets with a through and the phase difference is 180
What is refractive index
The ratio of the speed of light in a vacuum compared to the speed of light in a material
What is the calculation to calculate refractive index
n=c over v
What are the requirements for total internal reflection
The angle of incidence has to be greater than the critical angle and n1 has to be bigger than n2 ( more dense to less dense)
What is excitation
When the electrons absorb the wave as light and they jump up levels
What is dexecitation
The electrons fall back down to their ground energy level and they release energy as light
What is the distance of the first harmonic
4m
What is the distance of the second harmonic
2m
What is the distance of the third harmonic
1.5m
Describe bluetooth
lower power device to device links range up to 10m, the frequency is about 2.4 to 2.485
What are the advantages of microwaves
they can pass through the ionosphere
has better satellite communication
has a higher bandwitdth
What are the disadvantages of microwaves
transmission is affected by fog and rain
cannot communicate with vessels underwater
can be only be used in a line of sight
what are the advantages of radiowaves
can reach receivers out of site of the transmitter
can reflect off the ionosphere
what are the disadvantages of radiowaves
low bandwitdth
cannot carry as much information
it is also subject to interference
what are the advantages of digital signals
signals can be regenerated so is there is no loss of information
signals can carry more information because the signal is more multiplexed
there is less energy wasted because of total internal reflection
what are the disadvantages of digital signals
they are easily damaged because they are so fragile and brittle
poor joints lead to poor signal strength so the signal is poor
information can be scrambled because of sampling errors
what are the advantages of the analogue signal
it is best fitted for audio and video transmission
it posesses higher density
its easier in processing
what are the disadvantages of the analogue signal
data can be corrupted in analogue signals
it is quite difficult to synchronize an analogue sound
it also posess lower quality than digital
what are the advantages of infrared
does not interfere with other devices as the frequency is higher than bluetooth
has better quality and communication between devices due to higher frequency
what are the disadvantages of infrared
needs a line of sight
works with one device at a time
sunlight will interfere with the signal
what are the advantages of bluetooth
does not need to be in direct line of sight
bluetooth can be used on more than one device at the same time
what are the disadvantages of bluetooth
low bandwidth
interference with other bluetooth devices on similar radio frequencies if close by
How do fibre optics work?
transfer information using pulses of light. Each pulse undergoes total internal reflection down the fibre optic cable. The core must be as transparent as possible to prevent any attenuation. Cladding is used to protect the core to prevent cross over between cables. This allows for total internal reflection to take place. It must have a lower refractive index index than the the core.
True or false, waves in a string use longitudinal waves?
False, they use transverse waves
