Sound

Question 1

Sound waves

Answer 1

Sound waves consist of vibrating molecules. They are a type of longitudinal wave

Sound waves require a medium to travel through
If there are no molecules (e.g. in a vacuum) then the sound can’t travel

The range that humans can hear is 20 Hz to 20 000 Hz
The speed of sound is between 330-350 m/s

Sound travels faster in solids than in liquids and gases
Faster in liquid than in gases

The reflection of a sound wave is called an echo

Question 2

How does changes in amplitude and frequency affect the loudness and pitch of sound waves

Answer 2

Greater amplitude = louder sound
Greater frequency = higher pitch

Question 3

Ultrasound

Answer 3

A sound with a frequency higher than 20 kHz

Question 4

Experiments to determine the speed of sound

Answer 4

Two people stand a distance of around 100m apart
The distance between them is measured using a trundle wheel
One of the people has two wooden blocks, which he bangs together above his head
The second person has a stopwatch which he starts when he sees the first person banging the blocks together and stops when he hears the sound
This is then repeated several times and an average value is taken for the time
The speed of sound can then be calculated using the equation

Speed of sound = distance traveled by sound/ time taken

Question 5

Uses of ultrasound

Answer 5

non- destructive testing of materials, medical scanning of soft tissue

Question 6

Sound in states of matter

Answer 6

Sound waves travel faster in solids than in liquids and slower in gases

Solids (fastest)
Liquid
gases (slowest)

Question 7

Sound equation

Answer 7

Speed of sound = distance travelled/time.

Question 8

Speed of sound

Answer 8

In air - 330 m/s - 350m/s
In water - 1500 m/s
In steel - 5000 m/s