Activity 3 - Standing Waves

Activity objectives

A. To understand how a standing wave on a string is produced.

B. To determine the relation between the frequency and the wavelength of the standing wave on a string.

C. To determine the speed of sound using a closed tube.

D. To determine the resonance frequency at a fixed closed tube length.

E. To prepare for a practicum report.

Recall

What is wave?

What is the difference between transverse and longitudinal waves?

How waves are produced?

PART A

Questions:

i. Is the travelling wave on a string transverse or longitudinal? Mechanical or electromagnetic waves?

ii. What is a standing wave?

iii. How is a standing wave formed?

PART B

n ---- f (Hz) ------- number of envelope ----- wavelength (m)

What is the relation between the frequency and wavelength?
What is the relation between the fundamental frequency and the higher frequencies which can produce a standing wave?

Questions:

Can a standing wave produced in any frequency?

Part C

Differentiate between closed and open tubes.
You should have watched the following youtube (https://www.youtube.com/watch?v=xrF7ZmBG-9U). Otherwise, please revise after this activity.
Generate 440 Hz sound using the app. Bring it close to the tube ends (at the resonance tube opening, as shown below).
Adjust the water level until you hear the loudest sound. Record the length of the air column.
Calculate the sound velocity.

PART D

The theoretical value of sound velocity in air is 343 m/s. Calculate the resonance frequency if the tube length is 0.30 m
Verify your answer experimentally.