5.8 — answers

• Natuurkunde / Scheikunde
• Middelbare school
• vwo
• Leerjaar 1

1) Match the words with the definitions

(The colors match the sentence to the word)

• A region where particles are closer to eachoher is called a...

• The solid, liquid or gas the sound wave is moving through is called the...

• A reaion where the particles are far apart in a sound wave is called a...

• A sound wave is produce by something that is...

• Vibrating.

• rarefaction.

• compression.

• Medium.

2) Think about what happnens when you are talking. Decide wheter each of these statemnts is ture or false.

a. The air moleules move away from your mouth as you talk. True or false.

b. The sound wave makes the molecules in the air move backwards and forwards as you talk? True or false.

c. The sound wave makes the molecules move up and down as you talk. True or false.

3) The speed of sound in steel is 500 m/s, in water is 1500 m/s, but in air only 330 m/s,

 wordss Copy and complete the sentences below, using these words or phrases to fill in the gaps. Some owrds or phrases are not needed.

Closer together,    Further appart,    Less,    More

• The speed of sound in water is faster than the speed of sound in air because in water the particles are Closer than they are in air.
• The speed of sound in air is slower than the speed of sound in steel ecaus in steel the particles are Closer than they are in air.
• A sound made underwater will take Less time to travel a certain distance than a sound made in air.

4) The table shows the speed of sound in each of siex materials. Use the table and the information in question 3 to answer the questions below.

Material	Speed of sound (m/s)
A	4000
B	1207
C	1497
D	259
E	6420
F	435

a. Which two materials are probably liquids? B and C

b. Which two materials are probalby gases? D and F

c. Which two materials are probalbly solids? A en E

d. In which material are the particles closest together? E 

e. In which material are the partciles furthest apart? D

5) Look at the arrows on the diagram (see book for diagram, page 108 question 5).

Copy the table and tick the correct columns to show wether each arrow shows the wavelength, the amplitude, or neither.

Arrow	Wavelength?	Amplitude?	Neither?
A		v
B			v
C		v
D	v
E			v
F	v

6) A boy is whisteling a note that has a frequency of 1500 Hz.

a. Explain what a frequency of 1500 Hz means.  

A vibration of 1500 waves per second.

b. What would change about the sound he would hear if he whistledf at 2000 Hz?

It would have a higher pitch

7) Rani used a sound-level meter to survey the noise at different places and time during the day. Here are hre results

• By the road on the way to school: 70 dB
• sitting in a classroom: 50 dB
• Playing with friends: 80 dB
• Reading a book: 40 dB

a. What is meant by dB? Decibel.

b. Which sound would sound the loudest? Playing with friends

c. Rani's brother likes to listen to very loud music on his headphones. Describe two things that he could do to reduce the siks of damaging his hearing. Lower down the loudness of the sound, listen through speakers, listen to it for short times.

8) A teacher uses an oscilloscope to display some sound waves. The sounds shown are either loud or soft and eigher high or low pitched. Match the number to the letter in the pictures below.

See the book for the table with the images and the descpritons

1 with D

2 with C

3 with A

4 with B

9) For each statement about ultrasound, write 'true' or 'false'.

a. Ultrasound can be used to see an unborn baby. True or false.

b. Ultrasound is sound with a frequency greater than 2000 Hz. True or false.

c. Ultrasound is very-high-frequency sound. True or false.

d. Ultra sound cannot be heard by humans. True or false.

10) A fisherman uses sonar to find a shoal of fish. A pulse of ultrasound is sent out and the reflection is detected 0.4 seconds later.

a. How long did it take the sound to travel from the boat to the fish? 0.2 seconds

b. The seed of sound in water is 1500 m/s. How far below the boat are the fish? 

Given: v = 1500 m/s     t = 0.4 s

Asked: How far below the boat are the fish?

Formula: v= s/t     s= v * t

Calcualtion: s = 0.2 * 1500 = 300 m

Answer: The fish are 300 meter below the boat.

c. Somtimes fisherman will see another signal on the sonar after they dected the echo from the fish. Why? The sound pulse can hit another. schoal of fish, reflecting another echo.

11) Adami is watching a thunderstorm. She counts 4 seconds between seeing the lighting and hearing the thunder. The speed of sound in air is 330 m/s.

a. How far away is the storm?

Given: v = 330 m/s     t = 4s 

Asked: How far away is the storm?

Formula: v= s/t    s= v * t

Calcualtion: s = 4 * 330 = 1320 m

Answer: The storm is 1320 meters away

b. What assumption has Adami mad to do this calculation? 

That she would get her measurments right in one try.

12) A teacher uses an oscilloscope to show the same note being played on a saxophone and a vilon. Here is what is shown on the screen: 

(see the book)

a. How can you tell that they are playing the same note?

The peaks and the valleys of the wave are the same.

b. How can you tell that they are two different instruments?

Their sound waves have a different form.