CHAPTER 14

What is a wave?
a periodic disturbance of the particles of a substance that may be propagated without net movement of the particles, such as in the passage of undulating motion, heat, or sound.

What are the 2 types of waves?
Longitudinal and transverse.

For transverse waves the displacement of the medium is perpendicular to the direction of propagation of the wave. A ripple on a pond and a wave on a string are easily visualized transverse waves.


In longitudinal waves the displacement of the medium is parallel to the propagation of the wave. A wave in a "slinky" is a good visualization. Sound waves in air are longitudinal waves.

Transmitted waves are refracted or diffracted: Refraction occurs when a wave crosses a boundary from one medium to another. A wave entering a medium at an angle will change direction. Diffraction refers to the "bending of waves around an edge" of an object.

HOW DO WE CALCULATE THE VELOVITY OF A WAVE?

• velocity = frequency x wavelength.

Constructive interferences occur when two waves combine (add up) by the superpostition principle.


Destructive interferences occur when the crest of one wave interferes with the trough of another. Amplitudes are subtracted.

Imagine watching as water waves move past a post at the pier. If you count the number of crests passing the post for 10 s, you can determine the frequency of the waves by dividing the number of crests you count by 10 s. If you measure the distance between crests, you can find the wavelength if the wave. But how fast are the water waves ,moving?