Reflection
• When waves encounter a barrier that cannot
absorb or transmit their energy, the energy is
“reflected” by the barrier
• The angle at which the wave ray is reflected from
the barrier is equal to the angle at which it
approached the barrier (both “from the normal”)
• Smooth surfaces cause “specular” (bright, sharp)
reflection, and rough surfaces cause “diffuse”
(sheeny, fuzzy) reflection
Reflection Diagrams
Interference
• In addition to interacting with matter, waves also
interact with other waves
• Multiple waves traveling through the same place
“interfere” with each other – the individual wave
vibrations combine into a single wave
• When “like” vibrations (+/+ or -/-) combine, the
resulting vibration has a larger magnitude
• this is called “constructive interference”
• When “unlike” vibrations (+/-) combine, the
resulting vibration has a smaller magnitude
• this is called “destructive interference”
Interference Diagrams
Standing Waves
• When a wave of the right frequency is reflected from
a fixed boundary, a “standing wave” can be created –
the pattern of the wave is stationary
• Some locations have total destructive interference
• these parts of the wave have no displacement
• they are called “nodes”
• Other locations have total constructive interference
• these part of the wave have the most displacement
• they are called “antinodes”
Standing Wave Diagrams
• The two ends of a standing wave are always nodes
• The number of nodes is always one greater than the
number of antinodes