A2 principle of optical fibres

refractive index

number representing the bending of light the it passes from one medium to another because the. medium has gone denser

equation of refractive index

sin I / sin r (sin I is angle of incidence and sin r is the angle of refraction)

or

c / v (c is speed of light in vacuum, v is speed of light in material)

total internal reflection

hen light is completely reflected inside the medium instead of the light leaving the medium

when does total internal reflection occur

the light travels from a higher refractive index to a lower refractive index OR when the angle of incidence is greater than the critical angle

critical angle

the incidence angle that produces a refracted ray that refracts 90 degrees to the normal

critical angle fornula

sin (C) = 1 / n

(C is critical angle)

(N is refractive index)

optical fibre

a very thin stand of glass or plastic that carries light signals

what is the optical fibre made up of

core (the centre where the light travels)

cladding (the outer layers surrounding the core)

why is cladding used

since the cladding has a lower refractive index than the core, this is the conditions for the total internal reflection.

how is optical fibres used in engineering (+ benefits)

used in

• inspections inside aircraft engines

• inspecting pipes

• inspecting machinery

benefits

• flexible

• can reach to difficult areas

how is optical fibres used in communication (+ benefits)

used in

• internet

• telephone network

• broadband

benefits

• high bandwidth

• fast data transfer

• low signal loss

how is optical fibres used in medicine (benefits)

used for

• doctors can see what is inside the patient without doing a major surgery

benefits

• minimally invasive

• flexible

• produces clear image

analogue signal

a continuously varying signal

characteristics of analogue signal

• smooth waveform

• affected by noise

• quality decreases over distance

Digital signal

uses binary (010011010)

characteristic of digital signal

• less affected by noise

• can be regenerated

• more reliable for communication

how fast does an electromagnet waves travel at a vacuum?

3.0 × 10⁸ m/s

inverse square law

I = intensity (watts per square meter, W m^-2)

R = the distance from the source (meters, m)

K = constant that stays a constant as long as the source stays the same (if constant then k is 1)

as the distance increases the intensity decreases

electromagnetic spectrum from lowest frequency to highest freqneyc

radio waves

microwaves

infrared radiation

visible light

ultraviolet

x rays

gamma rays

what is the relationship between frequency, energy and wavelength)

as the frequency increases, the energy increases and the wavelength decreases.

what wave is used for satellite communication and GPS

microwaves

why do we use microwaves for satellite communication and GPS

because microwaves can pass through the atmosphere and can carry large amounts of data

what wave is used for mobile phones

microwaves / radio waves

why do we use microwaves and radio waves for mobile communication?

can carry digital information and can communicate with nearby cell towers

what wave do we use for bluetooth

radio waves in the microwaves regions

why do we use radio waves in the microwaves region for bluetooth?

short range communicate

what things uses bluetooth?

• headphones

• keyboards

• speakers

what is infrared raditation used for and why

TV remote controls because it is suitable for short range communication

characteristics of infrared radiation

• requires line of sight

• does not travel through walls well

what type of EM waves is used for wifi and why

microwaves because microwaves have higher frequency than radio waves, as well as it can carry digital data wirelessly.

benefits of wifi

• allows wireless communication

• allows multiple devices to connected to the internet

• fast data transfer over short distances

• no physical cable requires

limitations of wifi

• limited range compared with mobile phone networks

• signal strength decreases when distance away from the wifi sources increase

• walls and other obstacles can weaken the signal

• can experience interference from other wireless devices.