3A.1 Wave Basics

Question 1

What is a wave?

Answer 1

A transfer of energy through oscillations without any net movement of matter.

Question 2

What is the difference between mechanical and electromagnetic waves?

Answer 2

Mechanical waves require a medium, while electromagnetic waves do not require a medium.

Question 3

What is displacement in a wave?

Answer 3

The distance of a particle from its equilibrium position at a given time. (See Fig A / Fig B)

Question 4

What is amplitude?

Answer 4

The maximum displacement from the equilibrium position. (Shown in Fig A)

Question 5

What is wavelength (λ)?

Answer 5

The distance between two identical points on consecutive waves, such as crest to crest. (See Fig A)

Question 6

What is frequency?

Answer 6

The number of complete wave cycles per second. Unit: hertz (Hz).

Question 7

What is the period of a wave?

Answer 7

The time taken for one complete oscillation. T = 1/f.

Question 8

What is phase in a wave?

Answer 8

The position of a point in the wave cycle, measured in degrees or radians.

Question 9

What does a displacement-distance graph show?

Answer 9

The shape of the wave at a particular instant in time. (See Fig A)

Question 10

What does a displacement-time graph show?

Answer 10

The motion of one particle over time. (See Fig B)

Question 11

What is wave speed?

Answer 11

The speed at which the wave energy travels through a medium. Unit: m s⁻¹.

Question 12

What is the wave equation?

Answer 12

v = fλ, where v is wave speed, f is frequency, and λ is wavelength.

Question 13

How is the speed of sound measured using microphones and an oscilloscope?

Answer 13

Two microphones detect sound from a speaker. Move one microphone until the signals are in phase. The distance between microphones is one wavelength, then use v = fλ. (See Fig C)

Question 14

How does pulse-echo measurement work?

Answer 14

A wave pulse is sent out and reflected back, and the time taken for the echo is measured. Distance = vt/2 because the pulse travels to the object and back.

Question 15

What are some uses of pulse-echo measurements?

Answer 15

Sonar, medical ultrasound, radar, and animal echolocation. (See Fig D)

Question 16

Why is there a divide by 2 in pulse-echo calculations?

Answer 16

Because the measured time is for the round trip, so the wave travels twice the actual distance to the object.

Question 17

Why can wave speed be calculated using both v = distance/time and v = fλ?

Answer 17

Because frequency tells how many wavelengths pass per second, so both equations describe wave speed.

Question 18

What are the 5 key wave quantities?

Answer 18

Displacement, amplitude, wavelength, frequency, and period.