on your foldable label each tab with the following: **Look at board** on your foldable label each tab with the following: Interactions of Waves Reflection Refraction Diffraction Interference Standing Waves Doppler Effect Practice Questions

Waves can interact with other objects and with each other Interactions of Waves Waves can interact with other objects and with each other

Interactions of Waves with objects Reflection/Refraction/Diffraction

Reflection of waves Definition: The bouncing back of a wave when it hits a surface through which it cannot pass Light (an electromagnetic wave) and sound (a mechanical wave) waves can be reflected Example: sonar

Reflection – we see ALL objects because light waves reflect (bounce) off of objects and into our eyes!

Refraction of waves Definition: the bending of a wave caused by a change in its speed as it travels from one medium to another. DRAW Refraction of light:

Refraction of waves When white light hits a prism, the individual light waves change speed and bend at different angles, allowing each color to be seen. ***did the light wave speed up or slow down as it entered the prism?

Diffraction of waves Definition - When a wave moves around a barrier or through an opening in a barrier, it spreads out. Light waves diffract when they spread out after moving through the opening of a cloud. (DRAW in foldable!) You can hear conversations in other rooms because sound waves travel through an open door, and spread out down the hallway

Interactions of Waves with each other Constructive interference/ Destructive interference

INTERFERENCE When several waves are in the same location, they combine to produce a single, new wave that is different from the original waves. Interference can be constructive or destructive

CONSTRUCTIVE INTERFERENCE Constructive interference occurs when waves combine to make a wave with a larger amplitude. Think of constructive interference as waves “helping each other” or adding energies An example of constructive interference would be sound waves interacting from speakers at a concert

DESTRUCTIVE INTERFERENCE Destructive interference occurs when two waves combine to make a wave smaller in amplitude. Think of destructive waves as subtracting their energies/cancel each other out An example of destructive interference is sound canceling headphones

STANDING WAVES When two waves interfere that have equal wavelength and amplitude, but travel in opposite directions, they make a standing wave that looks like the diagram to the right The points in a standing wave that look pinched, are called nodes . Nodes are the places where waves have destructive interference, and cancelled each other out.

STANDING WAVES The widest points in a standing wave are called antinodes – these are the points where wave have constructive interference, and maximum amplitude is reached

THE DOPPLER EFFECT The change in frequency and pitch due to movement is called the Doppler Effect. DOPPLER EFFECT HAS TO DO WITH PITCH ONLY!!!!!!!!!!!! You can remember this by the name doPPler!! P stands for PITCH!!!!!

THE DOPPLER EFFECT Pitch is determined by the frequency at which a sound waves strike your eardrum. High frequency = high pitch low frequency = low pitch **what does this mean in terms of wavelength??

DOPPLER EFFECT When the object or sound source is moving, the frequency of the wave changes because the motion of the source affects the wavelength If an object is moving toward you the movement causes the wavelength to shrink/decrease – making frequency higher, making the pitch higher (when an object is coming TOWARD you, you hear a HIGHER PITCH)

If an object is moving away from you, the movement stretches the wavelength, making it longer, and making the frequency lower. (when an object is going AWAY from you, you hear a LOWER PITCH)

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DOPPLER EFFECT Who would hear a higher pitched sound? Why?

Constructive Interference Destructive Interference Terms to Know Reflection Refraction Diffraction Interference Constructive Interference Destructive Interference Standing Wave Node Antinode Sound Wave Vibration Intensity/Loudness Decibel Pitch Frequency Hertz Infrasound Ultrasound Doppler Effect