1. Define the following terms: wave, frequency, period

2. Draw a simple sine waveform and label these: amplitude, wavelength, crest, trough

Define the following terms: 1) Superposition2) Constructive interference3) Destructive interference4) Standing wave5) Nodes6) Antinodes

The Properties of Waves

1. Reflection

2. Refraction

3. Superposition

4. Diffraction

Have you ever experienced having a really bad cell phone reception in the middle of an open, urban area?

Question:

What happens when a wave meets another wave?

Wave + Wave = ?

Superposition (Interference)• Two waves can be ‘added’ together

• Constructive interference occurs when the two waves are in phase (i.e. crests meet crests, troughs meet troughs)

• Destructive interference occurs when they are 180 degrees out of phase (i.e. crests meet troughs)

Constructive Interference (Antinode)

Destructive Interference (Node)

Ruben’s Tube

Standing Wave, Nodes and Antinodes• Wave produced by the superposition of

two equal but opposite waves

• Antinodes – places where constructive interferences occur (double crest and double trough)

• Nodes – places where destructive interferences occur (crest + trough = zero displacement)

Interference Pattern• Anti-nodes are formed when constructive

interferences occur where two waves are in phase because the path differences are whole numbers (0, 1, 2, 3…).

• Nodes are formed when destructive interferences occur where two wave are 180o out of phase because the path differences are ½, 1½, 2½, 3½…

Constructive Interference

Destructive Interference

Anti Nodes (anti nodal line)

Nodes (nodal line)

Crest + CrestTrough + Trough

Crest + Trough

In phase 180o out of phase

Path differences are 0, 1, 2, 3, 4…

Path differences are ½, 1½, 2½, 3½…