WavesReflection and Refraction

When a wave moves from one medium into another (reaches a boundary)

◦Speed of the wave changes More dense slower less dense faster

◦Frequency stays the same

◦Wavelength changes

Waves at Boundaries

Vocabulary

◦ Incident wave/pulse The wave traveling towards the boundary

◦ Transmitted wave/pulse The disturbance that continues moving across

the boundary

◦ Reflected wave/pulse The part of the wave that bounces off the

boundary

Fixed end reflection◦ The end of the string is held in place◦ The reflected pulse is inverted

http://www.physicsclassroom.com/class/waves/u10l3a.cfm

Four Types of Wave Boundaries

Free end reflection◦ The end of the string is free to move up and down◦ The reflected pulse remains upright

Moving from a less dense to a more dense medium◦ The transmitted wave:

Slower Smaller wavelength

◦ The reflected wave: Same speed as incident Same wavelength as incident inverted

More dense to less dense◦ The transmitted wave:

faster larger wavelength

◦ The reflected wave: Same speed as incident Same wavelength as incident upright

Refraction◦ The change of speed causes a wave to bend

◦ Water waves moving from deep to shallow Waves move slower in shallow water The wavelength decreases as well

What happens when the incident waves hit a boundary at an angle?

Marching Studentsless dense to more densehttp://www.physicsclassroom.com/class/refrn/u14l1c.cfm - march

Marching Studentsmore dense to less dense

Marching Studentsa perpendicular approach

Fast slow◦ Bends towards the normal

Slow fast◦ Bends away from the normal

Incident wave is perpendicular to boundary◦ No refraction (bending)

Refraction Summary