Pupil sheet · Sound waves
Sound waves — return questions
Name ______________________ Date ____________
Use one to two weeks after the lessons. Keep the notes and the lesson closed.
1. identify
Without the reading: a struck tuning fork sends a note through still air to your ear. Match each thing to what it does while the note passes. The last two are Supplement. Use each description at most once; not every description is used.
Write the number of the matching option.
- travels with the sound all the way to your ear
- vibrates at right angles to the line the sound travels
- keeps vibrating after the strike
- a rarefaction, at lower pressure than still air
- vibrates along the line the sound travels
- is pushed and pulled by the prongs
- an empty gap with no air particles
- a compression, at higher pressure than still air
- Each prong of the fork: ______
- The air touching a prong: ______
- An air particle halfway to your ear: ______
- Supplement: a region where particles are crowded together: ______
- Supplement: a region where particles are spread out: ______
2. identify / state
A siren’s note rises from 700 Hz to 1.4 kHz while the amplitude of the sound gets smaller. The microphone position, timebase and gain stay fixed. Which row describes the change? Then state the approximate human audible range and whether both notes lie inside it.
| Row | Pitch | Loudness | Microphone trace |
|---|---|---|---|
| A | higher | louder | more cycles in the same time, taller |
| B | higher | quieter | more cycles in the same time, shorter |
| C | lower | quieter | fewer cycles in the same time, shorter |
| D | higher | quieter | fewer cycles in the same time, shorter |
Circle one answer.
- A
- B
- C
- D
Approximate audible range; are both notes inside it?
3. explain
Explain why removing air from a bell jar makes the sound outside fainter even while the bell visibly vibrates. Would a faint remaining sound prove that sound travels through a vacuum? Explain.
Why sound fades
What faint remaining sound means
4. state / calculate
(a) State the approximate range of the speed of sound in air. A walker sees a woodcutter’s axe hit a log and hears the thud 0.60 s later. Calculate how far away the woodcutter is, using 340 m/s. (b) Supplement: state the general order of sound speeds in solids, liquids and gases, from fastest to slowest.
(a) Air speed range, then the distance with working
(b) Supplement: general speed order