Wave Interactions

Wave Interactions Types of wave interactions Reflection Refraction Diffraction Interference

Reflection The bouncing back of a wave when it hits a surface. * NOTE: When waves hits a substance some of it is transmitted and some of it is reflected. Transmitted means to pass through This is why we can see objects and hear echoes.

Angles Angle of incidence – the angle between an incoming wave and an imaginary line drawn perpendicular to the surface of the barrier or new medium Angle of reflection – the angle between a reflected wave and an imaginary line drawn perpendicular to the surface off the barrier

Refraction The bending of waves as they pass through different mediums that cause the speed of the wave to change. Prism

Diffraction Change of direction of a wave when it hits an obstacle or edge. Sound diffracts well around corners Light does not diffract as much because their wavelengths are shorter Radio waves (especially AM) diffract when they encounter buildings. The radio waves bend around the building and the reception is still good on the opposite side. There is no "shadow" of the radio wave. 1 Sound waves diffract when they pass through a door. The sound spreads and fills the room on the other side of the door. Try standing out in the hallway by your classroom and talk. Can the people inside the class hear you? This is diffraction.  Helpful 21  Confusing 11 You can see visible light waves diffract through curtains. Look out at a street lamp. The light will spread left and right and up and down. This occurs because the light diffracts when it goes through the weave of the curtain. You may also notice that the light is alternately bright and dark as you look through the curtain. This is from interference. The bright places are where light waves are adding together. The dark places are where the waves cancel. With visible light, interference always occurs with diffraction.

Diffraction

Double Slit Experiment First conducted in 1801 by Thomas Young Light passed through a barrier with two slits (before it usually passed through a single slit to make the light coherent) The light diffracted through each slit Created interference pattern https://www.youtube.com/watch?v=Kdi4e76UvO8

Interference When 2 or more waves combine Two objects can’t occupy the same space at the same time, but waves can. There are 2 types of interference Constructive interference Destructive interference

Constructive Interference When the crest and trough of different waves match They combine to make a wave with larger amplitude Suppose you make two wave pulses on a stretched string, one comes from the left and one comes from the right. When the waves meet, they combine to make a single large pulse.

Destructive Interference When the crest of one wave meets the trough of another The results are a smaller amplitude or no amplitude What happens when one pulse is on top of the string and the other is on the bottom? When the pulses meet in the middle, they cancel each other out.

Standing Waves When waves combined they look like they are standing still, but are not. It is a combination of constructive and destructive interference

Standing Waves Nodes: any part of a standing wave that remains stationary. Antinodes: The positions on a standing wave where the largest amplitudes occur.