H2 Physics - Wave motion

Define a progressive wave

It is something which transports energy from one point to another in the direction of wave propagation

Define speed (for a wave)

It is the speed at which the wave shape moves

Define wavefront

It is a line or surface joining points on a wave that are in phase. The wave travels in a direction perpendicular to the wavefront.

Define a mechanical wave

It is a wave that requires a medium to propagate.

State the formula for the speed of a wave

v = fλ

State the 2 formulae for phase difference

ΔΦ = x/λ 2π = t/T 2π

Define intensity

It is the rate of transfer of energy per unit area normal to the direction of energy transfer of the wave

S

Define a plane wave

It is a wave whose wavefronts are parallel planes normal to the direction of energy transfer

State how the intensity of a plane wave behaves

Intensity of plane waves remain constant

Define a cylindrical wave

It is a wave whose wavefront form a family of coaxial cylinders

State how the intensity of a cylindrical wave varies with distance

It is inversely proportional to the distance

Define a transverse wave

It is a wave in which its particles oscillate in a direction perpendicular to the direction of energy transfer.

Define a longitudinal wave

It is a wave in which its particles oscillate in a direction parallel to the direction of energy transfer

State the 3 properties of an EM wave

• They do not require a medium to propagate

• They travel at 3.00×10⁸ ms^-1 in a vacuum

• They are transverse waves and hence can be polarised

Define the direction of polarisation of light

It is the direction of oscillation of the electric field vector

State the intensity of the polarised light after passing through a polarising filter when it entered unpolarised

I = I₀/2

State the equation for Malus' Law

I = I₀cos²θ