5.1-5.3 - Refraction and Total Internal Reflection (AQA A Level Physics )

Which wave property always remains constant when a wave travels from one medium to another?

Frequency

When entering a material with a higher refractive index what happens to wave speed?

decreases

When entering a material with a lower refractive index what happens to wavelength?

increases

What is the definition of the refractive index of a material

Speed of light in a vacuum/Speed of light in material

What are the angles of incidence and refraction measured relative to?

The normal to the boundary

Which way do waves refract when entering a material with a higher refractive index?

Toward the normal

Which way do waves refract when entering a material with a lower refractive index?

Away from the normal

What is the angle of refraction at the critical angle?

Ninety degrees

What are the conditions required for total internal reflection of a wave?

Wave must be travelling in a material with a higher index and meeting a boundary with a material of lower refractive index. The angle of incidence must be greater than the critical angle.

What is material dispersion in optical fibres?

The spreading out of pulses/loss of signal quality due to the different speeds at which different wavelengths travel in the core

What is modal dispersion in optical fibres?

The spreading out of pulses/loss of signal quality due to the different lengths of paths taken by rays in the optic fibre.

What is meant by a coherent bundle of optical fibres?

Each fibre is in the same relative position at either end of the bundle.

How can you prevents material dispersion in optical fibres?

Use monochromatic light

How can you prevent modal dispersion in optical fibres?

Use a narrow/monomode core.

Why is cladding usually required on an optical fibre?

To prevent damage to the core and to prevent signal transfer/corss-talk between touching fibres.