Chapter 12 and 14

Question 1

Sound waves

Answer 1

Is caused by vibration, sound won’t travel in a vacuum. Speed of sound is dependent on the medium (speed of air is 330m/s but varies due to air pressure and temp, denser medium = faster sound travel

Question 2

Sound wave structure and what it’s produced by

Answer 2

Sound waves are longitudinal and progressive in nature, can be only transmitted through a medium, and is produced by a series of compressions and rare fractions in the air. The air does move but the air molecules vibrate, when compressions and rare fractions enter your ear drum, they cause minute vibrations in the ear drum and you experience the sensation of sound

Question 3

Frequency

Answer 3

Number of compressions per second (F)

Question 4

Wavelength

Answer 4

Difference between 2 successive compressions

Question 5

V = f x (wavelenght)

Answer 5

V = velocity (m/s)
F = frequency (Hz)
Wavelength sign = wavelenght (m)

Question 6

Audibility

Answer 6

• human can hear sounds 20hz and 20000hz
• irregular vibrations cause noise. Sound of one frequency is called a pure note
• musical instruments produce regular vibrations characterized by loudness, pitch and quality

F = I/T

Frequency =F (hz)
Period = T (a)

Question 7

Pitch and amplitude

Answer 7

• a larger amplitude means a louder sound, smaller amplitude means softer sound
• a higher pitch sound has a higher frequency and smaller wavelength

Question 8

Effects on sound waves

Answer 8

Exhibit interference and diffraction effects

Reflected ( usually by hard surfaces) sound wave makes an echo. If the reflecting surface is less than 15m sways, it joins up with the original wave length and makes a reverberation which sounds longer. Modern concert halls are designed for optimal reverberation

Question 9

Wave

Answer 9

• disturbance that transfers energy through matter or space without mass / matter transfer
• electromagnetic waves don’t require a medium
• mechanical waves is produced by a disturbance (eg vibrating object and need a medium to propagate)
• transverse waves - a wave where displacement are perpendicular to direction of travel (direction of propagate eg:sea water)
• longitudinal waves - a wave whose displacements are parallel to its direction of travel (eg sound wave)

Question 10

Wave phenomena

Answer 10

• a wave speed changes when it endures a medium of different density (frequency does not increase)
• this means only the wavelength can change (increase when speed increases)
• refraction occurs when wave changes speed for example: water move slower in shallower water (thus the wavelength reduces)
• waves can also be reflected
• diffraction is bending of a wave when it enters a gap or obstacle
• displacements are parallel to direction of travel

Question 11

Wavelength

Answer 11

• distance between two consecutive crests or troughs

Question 12

Displacement

Answer 12

• distance of particles in a wave from mean or rest position

Question 13

Amplitude

Answer 13

Maximum displacement from rest position

Question 14

Velocity

Answer 14

Rate at which the wave moves (m/s)

Question 15

Phase

Answer 15

Constant difference between two waves

Question 16

Wavefront

Answer 16

Line where all particles in the wave are in phase

Question 17

Perical

Answer 17

T/S - time it takes to complete one wavelength (one cycle ) Si unit S

Question 18

Frequency (F)

Answer 18

Number of cycles (wavelength per unit time (Si unit : Hz)