Physics Test 4: Waves, Sound and Light

Question 1

What is a wave?

Answer 1

A disturbance or variation that travels through a medium

Question 2

What’s a longitudinal wave?

Answer 2

Particles move in the same direction as the energy. Think a slinky

Question 3

What is a transversal wave?

Answer 3

Particle is displaced perpendicular to the direction of energy. Think crests and troughs

Question 4

What’s the equation for the speed of sound?

Answer 4

V = 331.29 + 0.59t

t = temperature

Question 5

Frequency of a wave is determined by…

Answer 5

Frequency of the vibrating source.

Question 6

What is a mechanical wave?

Answer 6

Mechanical waves are waves which propagate through a material medium (solid, liquid, gas)

Question 7

What does wave speed depend on?

Answer 7

Elastic and inertial properties of the matter

Question 8

What happens during reflection?

Answer 8

The wave reflects at the angle it hits at. If it hit at a crest, it becomes a trough and vice versa

Question 9

What are real world examples of transverse and longitudinal waves?

Answer 9

Transverse: Water, light, radio
Longitudinal: Sound, earthquakes

Question 10

What does the size of a water wave depend on?

Answer 10

Amplitude

Question 11

What are the 3 types of waves?

Answer 11

Mechanical (longitudinal and transversal)
Electromagnetic ( x rays)
Matter waves (quantum)

Question 12

What is lamda?

Answer 12

Wavelength (from crest to crest or trough to trough)

Question 13

What is frequency?

Answer 13

of cycles / second

Question 14

What is velocity in respect to waves?

Answer 14

Speed each crest moves

Question 15

What is the period of a wave?

Answer 15

Time for one complete cycle (T = 1/F and F = 1/T)

Question 16

What is constructive interference?

Answer 16

When two waves overlap and their displacements are in the same direction (crest on crest, trough on trough)

Question 17

What is destructive interference?

Answer 17

When two waves overlap and their displacements are in opposite directions (crest on trough). They cancel each other out

Question 18

What is amplitude?

Answer 18

Distance between equilibrium and crest

Question 19

What determines amplitude?

Answer 19

Energy

Question 20

What is the wavelength for the first harmonic (the fundamental frequency) in an open tube?

Answer 20

L = 1/2 lamda

Question 21

What is the wavelength for the first harmonic in a closed tube?

Answer 21

L = 1/4 lamda

Question 22

What are nodes?

Answer 22

The point of max destructive interference is

Question 23

What is resonance

Answer 23

When two things vibrate that their frequencies are in phase

Question 24

What are beats?

Answer 24

Changes in amplitude when you have two waves of close frequency

Question 25

What is beat frequency?

Answer 25

The difference between the frequencies of two waves. Frequency of the beat = | F2 - F1|

Question 26

What does the spacing equal?

Answer 26

1/2 lamda in open tube
1/4 lamda in closed tube

Question 27

What is pitch?

Answer 27

The brain’s interpretation of frequency?

Question 28

What is the Doppler Affect

Answer 28

Apparent changes in frequency of a wave caused by relative motion between the source of the wave and an observer

Question 29

When frequency is larger there is a…

Answer 29

Higher pitch

Question 30

What is the formula for calculating the Doppler Affect?

Answer 30

F2 = f1 ( V + (vd) / V - (vs) )

V = Speed of sound
F2 = Shifted frequency
F1 = Original frequency
VD = Speed of detector
VS = Speed of source

If the sound is coming towards you, VS and VD are positive
If the sound is going away from you, VS and VD are negative