Telecommunications Flashcards
What is a wave
The transfer of energy from an origin to the desired output
What is the crest of a wave
The top of a wave’s curve
What is the trough of a wave
The bottom of a wave’s curve
What is the medium of a wave
The material which a wave passes through
What is the zero position of a wave
Where the medium would be if a wave was not passing through it
What is the amplitude of a wave
The height of the wave from either the zero position to the trough or the zero position to the crest
What is the wavelength of a wave
The distance taken for a wave to repeat itself (the length of one whole wave)
What is the period of a wave
The time taken for a wave to repeat itself (the time taken for one whole wave to pass a point)
What is the frequency of a wave
The number of complete waves that pass a point in one second
What is the equation of frequency
F = N/T
N= number of complete waves
What is the equation of period
P= T/N
What are the two main types of wave
+ transverse
+ longitudinal
What is a transverse wave
A wave in which the particles vibrate perpendicular to the direction of travel (up and down)
What is a longitudinal wave
A wave in which the particles vibrate parallel to the direction of travel
What is the speed of sound
340 metres per second
What is the speed of light
3x10 to the 8 metres per second
Is a sound wave transverse or longitudinal
Longitudinal
Is a light wave a transverse or longitudinal wave
Transverse
What is the equation of a wave when given frequency, velocity and wavelength
V = F x λ
What is colour dependant on
The frequency of the light Ray that we can see
What is the name of the colours that can be seen by the human eye
Visible light
What colours make up visible light
Red Orange Yellow Green Blue Indigo Violet
What colour has the highest frequency
Red
What is the name of the range of frequencies beyond visible light
The EM spectrum
What is the visible spectrum
Radio wave-> Microwave-> infrared -> visible -> ultraviolet -> x Ray -> gamma
Does the frequency increase or decrease as you go from radio->gamma
Increase
Does the wavelength increase or decrease as you go from radio->gamma
Decrease
Does the energy increase or decrease as you go from radio->gamma
Increase
What is the acronym for the EM spectrum
Real Men In Velcro Uniforms eXterminate Germs
If a light wave hits a surface, what can it do:
+ transmit through it
+ be absorbed by it
+ reflect off it
What is the normal of a reflecting Ray
A line that is at 90 degrees from the surface of reflection
What is the incident Ray of a reflecting Ray
The Ray of light that travels towards the point of reflection (light before reflection)
What is the reflected Ray of a reflecting Ray
The Ray of light travelling away from the point of reflection (light after reflection)
What is the angle of incidence of a reflecting Ray
The angle between the normal and the incident Ray
What is the angle of reflection of a reflecting Ray
The angle between the normal and the reflected Ray
What does the law of reflection state
That, on a flat surface, the angle of incidence is always equal to the angle of reflection
What are the two main types of lens
+ converging (convex)
+ diverging (concave)
What is a converging lens
One which is thickest in the middle and causes rays to come together and converge at the focal point
What is a diverging lens
One which is thickest on the outside and causes the rays to divert away from each other.
What is refraction
When a light Ray enters a medium of different density to the one it was previous travelling through.
E.g. air to glass
What happens during refraction
Its angle of travel changes as one of the edges of the Ray hits the medium first causing it to accelerate or decelerate depending on the density of the new medium.
What does the Ray do when travelling from a high —>low density
It bends away from the normal as the front edge accelerates
What does the Ray do when travelling from a low —>high density
It bends towards the normal as the front edge decelerates.
What is the angle of refraction
The angle between the refracted Ray and the normal
What is total internal reflection
When a Ray enters a two sided material that it cannot penetrate, chai’s from it to repeatedly reflect and bounce off the sides. For this to occur the Ray must enter the material at an angle greater than 90 degrees (the critical angle).
What is diffraction
When a wave bends around an obstacle or opening
If a wave has a large wavelength will it have a large or small angle of diffraction
Large
What occurs when a wave passes through a gap
It diffracts at both ends, creating a circular wave.
What does the energy of a wave depend on
It’s amplitude
During refraction, what always changes
The speed at which the Ray travels
During refraction, what sometimes changes
The direction of the Ray, depending on the difference in densities
What is the speed of any electromagnetic wave in air
3x10 to the 8 m/s
What is short-sightedness
When a person is unable to see objects that are far away, due to the fact that their pupils, focus the light before it reaches the retina
What is long-sightedness
When someone’s is unable to see close objects as their pupil does not focus the light before t reaches the retina
What type of lens is required to combat short-sightedness
A concave lens
What type of lens is required to combat long-sightedness
A convex lens
