Ch 11: Oscillations and Waves

Question 1

Perfect destructive interference between 2 waves may be described by saying they are directly opposite each other in amplitude, they are ___ degrees out of phase, or they are __ radians out of phase.

Answer 1

180 degrees
π

p. 393

Question 2

What is an antinode?

Answer 2

A point where a standing wave has its maximum amplitude.

p. 484

Question 3

How can you remember what a node is on a standing wave?

Answer 3

These are the points of NO Displacement.

p. 395

Question 4

What is the formula for the standing-wave wavelengths for two fixed ends?

Answer 4

λ_n = (2L)/n

(where n equals the harmonic number.)

Remember, the first harmonic is usually called the fundamental because once we know the fundamental wavelength λ₁, we automatically know all the other harmonic wavelengths, because:

• λ_{n =} λ₁ /n*
  p. 396

Question 5

In the same way that the fundamental wavelength can be used to figure out all the other harmonic wavelengths, the fundamental frequency can be used to figure out all the other harmonic frequencies using this equation:

Answer 5

• f_{n =} nf₁*
  p. 397

Question 6

The speed of a wave is determined by the type of wave, and the characteristics of the medium, NOT by the _________.

Answer 6

frequency

p. 390

Question 7

When a wave passes into another medium, its ____ changes, but its frequency does NOT.

Answer 7

speed

p. 390

Question 8

Does the amplitude of a wave depend on frequency, wavelength, or wave speed?

Answer 8

NO. Amplitude is determined only by how much energy is put into the wave to get it started.

p. 391