Skip to main content
Ch 17: Superposition
Knight Calc - Physics for Scientists and Engineers 5th Edition
Knight Calc5th EditionPhysics for Scientists and EngineersISBN: 9780137344796Not the one you use?Change textbook
Chapter 17, Problem 56

A 1.0-m-tall vertical tube is filled with 20°C water. A tuning fork vibrating at 580 Hz is held just over the top of the tube as the water is slowly drained from the bottom. At what water heights, measured from the bottom of the tube, will there be a standing wave in the tube above the water?

Verified step by step guidance
1
Step 1: Understand the concept of standing waves in a tube. Standing waves occur when the sound waves reflect off the water surface and interfere constructively with the incoming waves. For a tube open at one end and closed at the other (due to the water), the standing wave forms at specific heights where the tube length corresponds to odd multiples of a quarter wavelength.
Step 2: Calculate the speed of sound in air at 20°C using the formula: v = 331 + 0.6T, where T is the temperature in Celsius. Substitute T = 20 to find the speed of sound.
Step 3: Determine the wavelength of the sound using the relationship: λ = v/f, where v is the speed of sound and f is the frequency of the tuning fork (580 Hz).
Step 4: Identify the positions of the water heights that correspond to standing waves. For a tube open at one end, the standing wave forms at odd multiples of a quarter wavelength. Use the formula: L = (2n - 1)λ/4, where L is the length of the air column above the water, λ is the wavelength, and n is a positive integer (1, 2, 3, ...).
Step 5: Subtract the calculated air column lengths from the total tube height (1.0 m) to find the corresponding water heights. Repeat this for different values of n until the air column length exceeds the tube height.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
6m
Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Standing Waves

Standing waves occur when two waves of the same frequency and amplitude traveling in opposite directions interfere with each other. In a tube, standing waves form at specific frequencies, creating nodes (points of no displacement) and antinodes (points of maximum displacement). The conditions for standing waves depend on the length of the tube and the wavelength of the sound waves produced by the tuning fork.
Recommended video:
Guided course
07:58
Intro to Transverse Standing Waves

Fundamental Frequency and Harmonics

The fundamental frequency is the lowest frequency at which a system can oscillate, while harmonics are integer multiples of this frequency. In a closed tube, like the one described, only odd harmonics can form, leading to specific heights where standing waves occur. The relationship between the tube length and the wavelengths of these harmonics determines the heights at which standing waves can exist.
Recommended video:
Guided course
05:08
Circumference, Period, and Frequency in UCM

Speed of Sound in Water

The speed of sound in water is influenced by factors such as temperature and pressure. At 20°C, the speed of sound in water is approximately 1482 m/s. This speed is crucial for calculating the wavelengths of the sound waves produced by the tuning fork, which in turn helps determine the specific heights in the tube where standing waves can form as the water level changes.
Recommended video:
Guided course
05:17
Standing Sound Waves
Related Practice
Textbook Question

BIO Deep-sea divers often breathe a mixture of helium and oxygen to avoid getting the 'bends' from breathing high-pressure nitrogen. The helium has the side effect of making the divers' voices sound odd. Although your vocal tract can be roughly described as an open-closed tube, the way you hold your mouth and position your lips greatly affects the standing-wave frequencies of the vocal tract. This is what allows different vowels to sound different. The 'ee' sound is made by shaping your vocal tract to have standing-wave frequencies at, normally, 270 Hz and 2300 Hz. What will these frequencies be for a helium-oxygen mixture in which the speed of sound at body temperature is 750m/s ? The speed of sound in air at body temperature is 350m/s .

1
views
Textbook Question

A string under tension has a fundamental frequency of 220 Hz. What is the fundamental frequency if the tension is doubled?

2
views
Textbook Question

A 280 Hz sound wave is directed into one end of the trombone slide seen in FIGURE P17.55. A microphone is placed at the other end to record the intensity of sound waves that are transmitted through the tube. The straight sides of the slide are 80 cm in length and 10 cm apart with a semicircular bend at the end. For what slide extensions s will the microphone detect a maximum of sound intensity?

1
views
Textbook Question

Two loudspeakers emit sound waves of the same frequency along the x-axis. The amplitude of each wave is a. The sound intensity is minimum when speaker 2 is 10 cm behind speaker 1. The intensity increases as speaker 2 is moved forward and first reaches maximum, with amplitude 2a, when it is 30 cm in front of speaker 1. What is The amplitude of the sound (as a multiple of a) if the speakers are placed side by side?

2
views
Textbook Question

Microwaves with a frequency of 10.5 GHz are aimed downward into a flat-bottomed beaker that contains sunflower oil. A microwave detector above the beaker finds that there are strong reflections when the oil depth is 2.76 cm and 3.68 cm but at no depths in between. What is the index of refraction of sunflower oil at microwave frequencies?

1
views
Textbook Question

An old mining tunnel disappears into a hillside. You would like to know how long the tunnel is, but it's too dangerous to go inside. Recalling your recent physics class, you decide to try setting up standing-wave resonances inside the tunnel. Using your subsonic amplifier and loudspeaker, you find resonances at 4.5 Hz and 6.3 Hz, and at no frequencies between these. It's rather chilly inside the tunnel, so you estimate the sound speed to be 335 m/s . Based on your measurements, how far is it to the end of the tunnel?