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Question
What are the factors that affect the frequency of a vibrating string and how do they affect the frequency?
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Solution
The frequency (f) of a vibrating string is affected by:
(i) The length of the vibrating string. Frequency is inversely proportional to the length, i.e, `"f"α1/"l"`. it means, if length increases, frequency becomes less and if length decreases, frequency increases.
(ii) It is directly proportional to the square root of the tension, other factors remaining the same, e.g., if tension (or stretching force) is made 4 times, then the frequency will be `(sqrt4=2)` doubled.
(iii) The frequency, (f) is inversely proportional to the square root of the mass of unit length of the vibrating string, i.e., `"f"α1/sqrt"m′"` if m' is the mass of unit length of the string. Since m' = πr2.l, it shows that f is `α1/sqrt("r"^2)` or `1/"r"`, where r is the radius of the vibrating strings.
RELATED QUESTIONS
The diagram above shows a wire stretched over a sonometer. Stems of two vibrating tuning forks A and Bare touched to the wooden box of the sonometer. It is observed that the paper rider (a small piece of paper folded at the centre) present on the wire flies off when the stem of vibrating tuning fork B is touched to the wooden box but the paper just vibrates when the stem of vibrating tuning fork A is touched to the wooden box.
1) Name the phenomenon when the paper rider just vibrates.
2) Name the phenomenon when the paper rider flies off.
3) Why does the paper rider fly off when the stem of tuning fork B is touched to the box?
What are forced vibrations?
In following figure shows two tuning forks A and B of the same frequency mounted on two separate sound boxes with their open ends facing each other. The fork A is set into vibration.
- Describe your observation.
- State the principle illustrated by this experiment.
How do you tune your radio set to a particular station ? Name the phenomenon involved in doing so and define it.
When a body vibrates under a periodic force, the vibrations of the body are ______.
Differentiate between the following:
Radio waves and light waves.
On keeping the stem of a vibrating tuning fork on the surface of a table, a loud sound is heard. Give reason.
The diagram below shows three different modes of vibration P, Q and R of the same string of a given length.
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| P | Q | R |
- Which vibration will produce a louder sound and why?
- Which vibration will produce sound of maximum shrillness (or pitch) and why?
- What is the ratio of wavelength of vibrations P and R?
A string stretched between its ends is made to vibrate by placing the stem of a vibrating tuning fork at its one end. State three ways how you will increase the frequency of note produced by the string.
What do you understand by free (or natural) vibrations?
