Chapter 19 - Vibrations & Waves

Question 1

What is a Vibration?

Answer 1

A vibration is a periodic “wiggle” in time. When something moves forward and back, to and fro, side to side, etc., it is vibrating!

Question 1

What is a Wave?

Answer 1

A wave is a periodic “wiggle” in both time AND space.

Question 2

What kind of curve is in the shape of a wave?

Answer 2

Sine curves

Question 3

What does a Pendulum do? What is an example?

Answer 3

A pendulum swings back and forth (vibrates). A clock or legs are an example of a pendulum.

Question 4

What does the period of a Pendulum depend on?

Answer 4

The pendulum’s length! When covering longer distances, it also depends on gravity.

Question 5

What is the correlation between lengths and periods of a pendulum? (short vs. long)

Answer 5

Short length = short period.
Long length = long period.

Question 6

What is a Period?

Answer 6

A period is the time it takes for one complete vibration.

Question 7

How do you find the Amplitude of a Wave?

Answer 7

The amplitude is the distance from the midpoint of a vibration to the crest or trough of the wave.

Question 8

How do you find the Wavelength?

Answer 8

The wavelength is the distance from the crest of a wave to the next, or the trough of a wave to the next.

Question 9

What is the crest?

Answer 9

The crest is the top of a wave.

Question 10

What is the trough?

Answer 10

The trough is the bottom part between two waves.

Question 11

What is the relationship between frequency and period?

Answer 11

They are reciprocals of each other!
Frequency = 1/period
Period = 1/frequency

Question 12

What is meant by Frequency?

Answer 12

Frequency is how frequently a vibration occurs in a given time (usually seconds).

Question 13

What is the unit used to measure Frequency?

Answer 13

Hertz! (for example, 1 vibration/sec = 1 Hz)

Question 14

What is the source of ALL waves?

Answer 14

Vibrations!

Question 15

What is TRANSMITTED through waves?

Answer 15

ENERGY!!

Question 16

Explain what Wave Motion is and what it is NOT.

Answer 16

Wave motion is a disturbance in a medium.
Wave motion is NOT the motion of a medium itself!

Question 17

In what direction do TRANSVERSE WAVES move?

Answer 17

At right angles to the medium. (view slinky example)

Question 18

In what direction do LONGITUDINAL WAVES move?

Answer 18

The same direction as the medium. (view slinky example)

Question 19

What kind of wave is light?

Answer 19

Transverse!

Question 20

What kind of wave is sound?

Answer 20

Longitudinal!

Question 21

What is the Rarefaction?

Answer 21

The rarefaction is the stretched region between compressions in a longitudinal wave.

Question 22

What is the equation for Wave Speed?

Answer 22

wave speed = frequency x wavelength
OR
v = fλ

Question 23

What is Wave Interference?

Answer 23

Wave interference is when two waves meet while they’re traveling across the same medium. They can form Interference Patterns, which cause the effects of a wave to be increased, decreased, or neutralized.

Question 24

What is a Node(s)?

Answer 24

The place(s) of MINIMUM displacement or energy. It can be zero.

Question 25

What is a Antinode(s)?

Answer 25

The place(s) of MAXIMUM displacement or energy.

Question 26

Explain Constructive Interference.

Answer 26

Constructive Interference is when the crests of two waves overlap and produce a wave of increased amplitude as a result.

Question 27

Explain Deconstructive Interference.

Answer 27

Deconstructive Interference is when the crest of a wave and the trough overlap and the individual effects of both are reduced.

Question 28

Explain the Doppler Effect and give an example.

Answer 28

The Doppler Effect is the change in frequency due to the motion of the source or receiver of a wave/vibration. Only the FREQUENCY and the WAVELENGTH can be changed! The SPEED of a wave will always stay the same!

The Doppler Effect explains how police sirens get louder as they get closer to you. The sound waves are hitting your ears more frequently as they get closer to you, so they are louder.

Question 29

What is a Blue Shift and why does it occur?

Answer 29

A blue shift is when there is an increase in frequency. This is because blue is on the higher end of the color spectrum.

Question 30

What is a Red Shift and why does it occur?

Answer 30

A red shift is when there is a decrease in frequency. This is because red is on the lower end of the color spectrum.

Question 31

What does “supersonic” mean?

Answer 31

Supersonic is used to describe something that travels faster than the speed of sound.

Question 32

What does “subsonic” mean?

Answer 32

Subsonic is used to described something that travels slower than the speed of sound.

Question 33

What are Bow Waves?

Answer 33

Bow Waves are V-shaped waves that are produced when an object is moving on a liquid surface faster than the wave speed.

Question 34

What are Shock Waves?

Answer 34

Shock Waves are cone-shaped waves that are produced by an object moving at supersonic speed.

Question 35

What objects will produce a sound when they are moving faster than the speed of light?

Answer 35

Any object will!

Question 36

What causes Sonic Booms?

Answer 36

Shock waves cause sonic booms! They create overlapping waves that reach our ears as one single burst of sound.

Question 37

Why do we not hear objects at subsonic speed?

Answer 37

We don’t hear subsonic objects because they do not create overlapping waves. These sound waves reach our ears continuously and are perceived as such.