Standing Sound Waves

Subject Area

Sound waves

Age or Grade

9^th grade

Estimated Length

40 minutes

Prerequisite knowledge/skills

Waves, wavelength

Description of New Content

Standing sound waves

Goals

Students should understand that the wavelength of a standing sound wave corresponds to the pitch of the sound they hear.

Materials Needed

-a flute, or any other air instrument that plays tones by changing the size of the resonating cavity

-five tall glasses or bottles

WARNING: This unit is likely to get messy. Instead of using the bottles and water, one can use a slide whistle and ask students to calculate the length of the tube by subtracting the length of the slide from the length of the tube.

Procedure

Opener:

Produce different tones with the flute and note that different number of instrument holes covered produces different pitch.

Development:

Have students fill five glass bottles of water with different amounts of water. They can start with the first being filled up so there is 4 cm of empty space left.

In the worksheet, students will

1. draw the water in five bottles.

2. write the height of the empty space

3. rank the bottles based on the pitch of the tone produced by blowing in the tube.

4. relate the height of the empty part of the tube with the height of the pitch.

Close: Discussion of wavelengths of standing waves

Evaluation

The worksheet gets graded.

Extensions

Relate the length of the empty part of the tube with the length of a guitar string.

References