Universal Wave properties We will discuss the 4 universal properties of waves

The 4 properties Reflection Refraction Diffraction Interference

Reflection Bouncing back of a wave as it strikes a boundary A closer look

Refraction The bending of a wave as it passes the boundary between two media. Example: Pole in pool looks bent, eyeglasses.

Diffraction The bending or spreading of a wave as it passes an obstruction. Example: light go through keyhole or bending around a corner.

Interference When two or more waves share the same space at the same time. These waves both act independently on the medium Example: two radio stations at once.

Constructive Interference When two waves tend to do same thing to medium, the total effect builds up. This is know as constructive interference.

Destructive Interference When two waves tend to do opposite things to medium, the total effect builds up. This is know as destructive interference.

Noise Cancellation Destructive interference, if applied correctly, can be very useful. In an airplane, the engine noise presents a problem. Pilots can use special headphones mounted with a microphone the headphones creates a wave that is the inverse of the wave that represents the engine noise.

Noise Cancellation The wave is then played back through the headphones allowing destructive interference to produce a quieter background. Other applications for destructive interference are "quieting" cars and passenger sections in airplanes.

A sample problem A sound wave is emitted and its echo is heard 1.27 seconds later. How far did the sound wave travel? How far did the sound wave travel before it reflected back? USE V=340m/s d = 340 x 1.27 d= 432m R = d/2 R = 216m

A second sample problem A radio station emits a carrier wave at a frequency of 99.7MHz. What is the period of the wave? What is the wavelength of the wave? USE V=3 x 10 8 T = 1/f T = 1/99,700,000 T= or V = F 3 x 10 8 =99.7 x 10 6  3.01m