3.1- Progressive and Stationary Waves

Define frequency

the number of waves passing through a point per second

Define wavelength

The distance between two adjacent peaks on a wave

Define amplitude

the maximum displacement of a wave from its rest position

How can you find the time period of a wave using its frequency

T = 1/f

What is phase difference and what is it measured in?

Phase difference refers to the difference in the phase of two waves at a given point in time, often measured in degrees or radians. It indicates how much one wave is ahead or behind another in their cycle.

What is a longitudinal wave?

A wave in which the oscillation of the particles is parallel to the direction of energy transfer. They contain rarefactions (areas of low pressure) and compressions (areas of high pressure).

What is a transverse wave? Give examples.

Awave in which the oscillation of the particles is perpendicular to the direction of energy transfer. Examples include em waves and waves on a string.

Speed of em waves in a vacuum.

3 × 10^8 m/s

In an electromagnetic wave, how are the magnetic field and electric field arranged?

The electric field and magnetic field are perpendicular to each other and to the direction of wave propagation.

What does a polarising filter do?

Only allows light with oscillations in one plane

How is polarisation used as evidence of the nature of transverse waves?

Polarisation can only occur if a wave’s oscillations are perpendicular to its direction of travel.

How are polarisers used in antennas?

TV and radio signals are usually plane-polarised by the orientation of the rods on the transmitting arial, so the receiving aerial must be aligned in the same plane of polarisation to receive the signal at full strength.

What is a stationary wave?

A wave which transfers no energy and whose positions of maximum and minimum amplitude are constant.

What is a node?

A point on the stationary wave where displacement is 0.

What is an antinode?

A point on a stationary wave with maximum displacement.

What are the conditions for a stationary wave to be produced?

1) Waves are of the same frequency, wavelength and amplitude

2) Waves must be travelling in opposite directions

This happens mostly when a wave is reflected back onto itself.

How are stationary waves produced?

A stationary wave is formed from the superposition of 2 progressive waves, travelling in opposite directions in the same plane, with the same wavelength, amplitude and frequency.

Where the waves meet in phase, constructive interference occurs so antinodes form.

Where the waves meet completely out of phase, destructive interference occurs and nodes form.

Describe the first harmonic for a stationary wave with 2 closed ends.

Consists of 2 nodes at either end and an antinode in the middle.

Describe the second harmonic for a stationary wave with one open end and one closed end.

Consists of 2 nodes and 2 antinodes, with one of the nodes at the closed end and one of the antinodes at the open end.

What is a progressive wave?

A wave the carries energy from one place to another without transferring any material.