Chapter 11 - Waves

What is a progressive wave

A wave that transfers energy from one place to another without transferring matter.

Does matter travel with a progressive wave?

No. The wave transfers energy without transferring matter; particles oscillate about their equilibrium positions.

What’s the difference between transverse and longitudinal waves.

In a transverse wave, oscillations are perpendicular to the direction of energy transfer. In a longitudinal wave, oscillations are parallel to the direction of energy transfer.

What is wavelength?

The shortest distance between two points on a wave that are in phase.

What is frequency? Give the Unit

The number of complete oscillations passing a point per second. Measured in Hz.

What is amplitude?

The maximum displacement of a point on a wave from its equilibrium position.

State the wave equation and units of each quantity.

v=f x lambda, where v is in m s⁻¹, f in Hz and lambda

What is the phase difference between two points separated by one wavelength?

360 Degrees — they are in phase.

Define in phase

Define antiphase

In Phase - The particles or waves reach their maximum positive displacement (crests) and maximum negative displacement (troughs) at the same time and have the same direction of motion at the same time

Anti phase - One particle or wave reaches its maximum positive displacement (crest) at the exact moment the other wave reaches its maximum negative displacement (trough)

Define in phase

Define antiphase

In Phase - The particles or waves reach their maximum positive displacement (crests) and maximum negative displacement (troughs) at the same time and have the same direction of motion at the same time

Anti phase - One particle or wave reaches its maximum positive displacement (crest) at the exact moment the other wave reaches its maximum negative displacement (trough)

How do you calculate phase difference from separation?

Phase Difference = (Separation / Wavelength) x 360 Degrees

Define reflection

The change in direction of a wave when it reaches a boundary and remains in the same medium it’s travelling through

State the law of reflection.

The angle of incidence equals the angle of reflection, with both angles measured from the normal to the boundary.

Define Refraction

The bending of a wave at a boundary between 2 materials due to the difference in the density of the materials, causing it to speed up or slow down as it changes direction

What way does a wave bend as it moves into faster/less dense medium

Away from the normal

What way does a wave bend as it moves into a denser/ slower medium

Towards the normal

What happens to wavelength when a wave enters a medium where its speed decreases?

Wavelength decreases, because v=f x lambda and frequency remains constant.