PhET Activity for MS-PS4-1: Sound Waves

DIRECTIONS:
1. You should be on the main menu screen. Click on the 'Intro' icon to begin.
Take 2-3 minutes to explore the 'Intro' tab. Try moving the sliders for 'Frequency' and 'Amplitude' and observe what happens to the waves coming from the speaker. Click the play/pause button at the bottom. Do not worry about the questions yet, just explore.

QUESTION: Are you acquainted with the tools in this simulation?

DIRECTIONS:
1. If you haven't already, click the orange reset button in the bottom-right corner to set the simulation to its default state.
2. Observe the appearance of the waves at the default (medium) amplitude.
3. Drag the 'Amplitude' slider in the right panel all the way to the right (maximum).

QUESTION: What does increasing the amplitude of the sound wave do to its visual representation in the simulation?

DIRECTIONS:
1. Keep the Amplitude slider at maximum.
2. In the right panel, click the 'Listener Audio' checkbox to turn on the sound.
3. Slowly drag the 'Amplitude' slider from maximum all the way to the left (minimum) and back again.

QUESTION: A wave with a higher amplitude is perceived as ___ and carries more ___.

(a)  

DIRECTIONS:
1. Click the orange reset button.
2. Slowly drag the 'Frequency' slider all the way to the left to its minimum value (100 Hz).
3. Now, drag the 'Frequency' slider all the way to the right to its maximum value (1000 Hz).

QUESTION: As the frequency of the wave increases, its wavelength (a)   .

DIRECTIONS:
1. Click the orange reset button in the bottom-right corner.
2. Click on the 'Measure' tab in the bottom menu.

QUESTION: Based on the tools available (ruler and timer), describe a procedure you could use to calculate the speed of the sound wave.

DIRECTIONS:
1. Ensure you are on the 'Measure' tab with default settings (Frequency at 550 Hz).
2. Press the pause button (II) at the bottom of the screen to freeze the waves.
3. Drag the ruler from the toolbox on the right.
4. Align the '0 m' mark of the ruler with the center of one of the dark wave bands (a crest).

QUESTION: At the default frequency of 550 Hz, what is the approximate wavelength of the sound wave?

DIRECTIONS:
1. Press the orange reset button to reset the 'Measure' tab.
2. Drag the 'Frequency' slider all the way to the left to 100 Hz.
3. Press Play and then Pause to generate the new, longer waves.
4. Use the ruler to measure the new wavelength.

QUESTION: By decreasing the frequency, you observe that the wavelength of the wave (a)   .

DIRECTIONS:
1. Click the orange reset button to return to default settings.
2. Observe the wave at the default medium amplitude.
3. Next, slide the 'Amplitude' slider to its maximum value.

QUESTION: Based on the visual representation, increasing a wave's amplitude (a)   its energy.

DIRECTIONS:
1. Keep the Amplitude slider at its maximum position.
2. Imagine this wave has an energy of 4 units.
3. Now, move the Amplitude slider to the exact halfway point of the slider bar. This represents halving the amplitude.

QUESTION: If a wave with a certain amplitude has 4 units of energy, what will its energy be if you reduce its amplitude by half?

DIRECTIONS:
1. Click on the 'Two Sources' tab in the bottom menu.

QUESTION: Describe the pattern you see on the screen. What is happening where the waves from the two speakers meet?