1.6 Total Internal Reflection

What does TIR stand for?

Total Internal Reflection

What are the 2 conditions needed for TIR to occur?

1. The angle of incidence must be greater than the critical angle.

2. Must be travelling from more dense to a less dense medium.

What is the critical angle?

The angle beyond which the wave will be fully reflected at the boundary between two mediums.

What is the critical angle in terms of the angle of incidence and refraction?

The critical angle is the angle of incidence which produces a 90 degree angle of refraction.

i=c

What happens when the angle of incidence is less than the critical angle?

Mostly refraction occurs

Partial reflection

What form of information transfer makes use of TIR?

Optical fibres

Which waves are used to send information through optical fibres?

Infra red

Visible light

What are optical fibres made out of and why is it coated in plastic cladding?

- Optical fibres are made out of glass

- The cladding causes light to be confined to the core of the fibre by TIR.

Give 3 uses of optical fibres.

1. High-speed internet connections

2. Endoscopes

3. Carries information as pulses of light

What are 2 advantages of using optical fibres?

1. Great flexibility

2. Signals don't suffer from interference

What is a CT scan?

Computerised Tomography Scanner

- It is a medical scanner that uses X-rays to form detailed images of the inside of the human body.

- It is usually used for a medical diagnosis.

Which waves does CT scans use?

X-rays

Give 2 advantages for using a CT scan instead of an endoscope.

1. CT scans are non-invasive so don't involve the insertion of equipment into the body

2. CT scans can produce more detailed images on the internal organs.

Give an advantage of using an endoscope over a CT scan.

Endoscopes don't involve exposure to X-ray radiation, which in large doses can cause harm to body cells.

Make a comparison of using optical fibres and satellites for long distance communication.

- Optical fibres are point to point communication.

- Infra red signals sent by optical fibres do not suffer from interference unlike microwaves (e.g storms).

- The distance travelled via optical fibres is shorter than by microwave satellite.

- The speed of the infra red signal through the optical fibres is lower than the speed of microwaves through the air.