Waves interact and transfer energy in predictable ways

How forces cause waves How waves transfer energy How waves are classified

wave a disturbance that transfers energy from one place to another waves transfer energy over distance without moving matter the entire distance

Where Do Waves Get Energy? Vibration-Any movement that follows the same path repeatedly. An object that is vibrating is moving. A force causes the vibration. An object that is moving has energy. A vibrating object gives off some of its energy to nearby particles. This movement of energy from a vibrating source outward is a wave. Waves get their energy from a vibration.

Vibrations Example: The top of a drum vibrates after it is struck by a drum stick. It moves up and down several times creating sound. Example: Your ear drum vibrates in response to sound which enables you to hear.

medium any substance that a wave moves through ex. water, the ground, a rope, air

Waves Through Matter and Space Medium-Matter or substance through which a wave is transmitted. Water is a medium for ocean waves. Air is a medium for sound waves. All phases of matter solids, fluids, plasmas, can act as a medium.

mechanical waves any wave that transfers energy through matter (must have matter to work) wavelength

transverse waves the direction in which the wave travels is perpendicular to the direction of the disturbance

longitudinal wave the wave travels in the same direction as the disturbance

Warm - up What is the difference between reflection and refraction?

Warm - up What is the main difference between a mechanical and an em wave?

how amplitude, wavelength and frequency are measured how to find a wave’s speed

Amplitude the distance between a line through the middle of a wave and a crest or trough. see p. 17

wavelength the distance from crest to crest or trough to trough

frequency the number of wavelengths passing a fixed point in a certain amount of time (usually a second) Waves / second (hertz)

Wave speed speed = wavelength x frequency S = λ ∙ f

warm-up Draw a transverse wave. Label a crest, trough, wavelength, and amplitude.

5 QQ Draw a transverse wave. Label the wavelength. Label the amplitude. Draw a low amplitude transverse wave and a high frequency transverse wave. Draw a longitudinal wave, label the rarefactions.

NameAmplitudeWavelengthFrequencyWave Speed

How waves change as they encounter a barrier What happens when waves enter a new medium How waves interact with other waves

reflection the bouncing back of a wave after it strikes a barrier

refraction the bending of a wave as it enters a new medium occurs because waves travel at different speeds in different mediums

diffraction the spreading out of waves through an opening or around an obstacle

interference waves interact with other waves they can add energy to, or take energy away from each other the meeting and combining of waves

Suppose that you create a wave by moving a rope up and down. What will happen if you increase the energy you put into the rope? What will happen if you increase the speed of the motion? amplitude, frequency, wavelength

wavelength frequency amplitude reflection refraction diffraction medium disturbance force hertz mechanical wave wave transverse wave longitudinal wave interference crest trough vibration constructive interference destructive interference wave speed compression rarefaction waves / second