Chapter 11 - Waves

Question 1

What is a wave?

Answer 1

An energy carrying pulse (disturbance) that travels through a medium, away from its source.

Question 2

What happens as a wave travels away from its source?

Answer 2

The wave’s intensity decreases as it travels away from its source because the energy gets more and more spread out.

Question 3

What do waves transport?

Answer 3

Waves transmit energy from one place to another without transporting matter.

Question 4

Properties of transverse waves

Answer 4

• particles in the medium move perpendicular to the
  direction of the wave.
• zig zags up and down
• do NOT travel though fluids

Question 5

Properties of longitudinal waves

Answer 5

• particles in the medium move in the same direction
  as the wave.
• travels in pulses in a straight line
• do travel though fluids
• Ex: sound waves

Question 6

What are compressions and rarefractions? Which type of wave has them?

Answer 6

Longitudinal waves have compressions and rarefractions. Because these waves travel in pulses, there are places where the air molecules are pressed tightly together (compressions) and places where the air molecules are more “rare” and spaced out (rarefractions).

Compressions - higher air pressure
Rarefractions - lower air pressure

Question 7

Period

Answer 7

The time interval after which a wave repeats itself; seconds per vibration.

Question 8

Frequency

Answer 8

How often the pattern of motion repeats itself; the number of to and fro motions in a given time.

Question 9

Equation for period and frequency? Units?

Answer 9

period = 1/frequency

period = seconds; frequency = Hertz

Question 10

Parts of a wave

Answer 10

Crest, trough, amplitude, wavelength, midpoint

Question 11

Principle of superposition

Answer 11

When 2 or more waves overlap, the net disturbance equals the individual disturbances of the waves added together.

Question 12

What is reflection?

Answer 12

When a wave hits an abrupt boundary between mediums and bounces off.
- Ex: echo

Question 13

What is refraction?

Answer 13

When a wave hits another wave or a change in the medium and bends.

Question 14

What is constructive interference?

Answer 14

• 2 identical waves overlap and travel in the same
  direction
• add together to make a bigger wave

Question 15

What is destructive interference?

Answer 15

• 2 waves with same frequencies but opposite crests
  and troughs
• cancel each other out
• 0 amplitude

Question 16

What is a standing wave?

Answer 16

When a wave is sent out, reflects straight back, and knocks/cancels the incident wave out.