Waves and Sounds

Question 1

Strings and Pipes

Open pipe, closed pipe and fixed string ends and wavelength formulas

Answer 1

Question 2

Properties of waves

Transverse versus longitudinal waves

Answer 2

Tranverse waves propagate perpendicular to its oscillations while longitudinal waves propagate parallel to oscillations.

Light is a transverse wave while sound is a longitudinal wave

Question 3

Properties of waves

Wavelength (λ)

Answer 3

Distance between two peaks on a wave diagram.

Question 4

Properties of waves

Frequency (f)

Answer 4

Number of wavelengths that pass a given point per second. Unit is s^-1

Question 5

Properties of waves

Period (T)

Answer 5

Question 6

Properties of waves

Wave velocity formula

Answer 6

Question 7

Properties of waves

Angular frequency (ω)

Answer 7

Question 8

Properties of waves

Intensity

Answer 8

Question 9

Produced by vibrations in a medium. Cannot propagate through a vacuum.

Answer 9

Sound

Question 10

Sound

Velocity by phase

Answer 10

Among phases of matter, sound travels fastest in solids (most “stiff”) and slowest in gases
Within a given phase of matter, such as when comparing a solid to another solid, the relationship works differently: velocity of sound is inversely proportional to density of the medium such that velocity increases as density decreases.

Question 11

Sound

Doppler effect

Answer 11

Perceived frequency differs from actual frequency when the source and observer are changing relative positions.

Moving toward each other increases the frequency

Moving away from each other decreases the frequency

Question 12

Sound

Doppler effect formula

Answer 12

Question 13

Sound

Intensity of sound formula

Answer 13

Question 14

Sound

Attenuation

Answer 14

Attenuation is the loss of intensity as sound travels through a medium
Also known as damping
Attenuation increases with greater distance traveled or with more elastic / less dense mediums

Question 15

Sound

Ultrasound

Answer 15

Ultrasounds produce images by taking advantage of the Doppler effect, with the ultrasound probe as a Stationary observer with velocity of 0.
Since the velocity of the observer is 0, the motion of the object being imaged can then be derived from the remainder of the variables in the Doppler equation (difference in frequencies and velocity of sound)

Question 16

Interactions of waves

When two waves interact in phase, the resultant wave will have amplitude equal to the sum of the individual amplitudes.

Answer 16

Constructive interference

Question 17

Interactions of waves

When two waves interact out of phase, the resultant wave will have amplitude equal to the difference of the individual amplitudes.

Answer 17

Destructive interference

Question 18

Interactions of waves

Standing waves

Answer 18

Waves that oscillate vertically without traveling horizontally. They are the result of interference from two waves of identical frequency going in opposite directions.

Question 19

Interactions of waves

Nodes and antinodes

Answer 19

Antinodes are the points of maximal displacement or oscillation; nodes are the points of zero oscillation.

Question 20

Interactions of waves

Resonant frequency

Answer 20

When a force is applied at the resonant frequency, it increases the amplitude.
Example: pushing a person on a swing.