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Wave Characteristics

Wave characteristics are measurable features of a wave, mainly wavelength, frequency, time period, and amplitude.

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Student-friendly explanation

Wavelength is the distance between two consecutive compressions or two consecutive rarefactions. Frequency is the number of vibrations per second, measured in hertz. Time period is the time for one complete vibration. Amplitude is the maximum displacement from the mean position and is linked with loudness.

How to write this in exams

  1. 1

    Start with the exact idea

    Wave characteristics are measurable features of a wave, mainly wavelength, frequency, time period, and amplitude.

  2. 2

    Then show how to use it

    List given quantity. Use f = vibrations/time for frequency. Use T = 1/f for time period. Write correct units in the final answer.

  3. 3

    Add one concrete example

    If a tuning fork vibrates 256 times in one second, its frequency is 256 Hz and its time period is 1/256 s.

  4. 4

    Avoid this incomplete answer

    Wrong answer: Frequency is 240 Hz for 240 vibrations in 3 s. This is wrong because the vibrations must be divided by time.

Definition

Wave characteristics are measurable features of a wave, mainly wavelength, frequency, time period, and amplitude.

Example

If a tuning fork vibrates 256 times in one second, its frequency is 256 Hz and its time period is 1/256 s.

Rule to remember

Frequency f = number of vibrations/time; time period T = 1/f; wavelength λ is distance between consecutive compressions or rarefactions.

Memory hook

Frequency counts how often; time period tells how long for one.

Examples and method

Worked example

A source completes 240 vibrations in 3 s. Frequency = 240/3 = 80 Hz. Time period = 1/80 s = 0.0125 s.

Method to apply

List given quantity. Use f = vibrations/time for frequency. Use T = 1/f for time period. Write correct units in the final answer.

Diagram support

Label compression, rarefaction, wavelength, and amplitude on a wave representation. Show wavelength between two consecutive compressions.

How CBSE asks it

Questions may ask definitions with units, identification from a graph, or simple calculation of frequency and time period.

Avoid common mistakes

Common confusion

Students often confuse frequency with amplitude. Frequency affects pitch, while amplitude affects loudness.

Common wrong answer

Wrong answer: Frequency is 240 Hz for 240 vibrations in 3 s. This is wrong because the vibrations must be divided by time.

Exam tip

Write units carefully: wavelength in metre, frequency in hertz, time period in second, and amplitude in metre.

Quick check

If a sound source completes 100 vibrations in 2 seconds, what is its frequency?

Its frequency is 50 Hz because frequency equals number of vibrations divided by time, so 100 divided by 2 is 50 vibrations per second.

Study the wave characteristics diagram carefully

Use the labelled diagram to keep wave characteristics clear in short answers and revision.

What this diagram makes clear

This diagram keeps the labels and direction of wave characteristics in the right order.

Where this helps in exams

Use this for labelled diagram work and short exam answers on wave characteristics.

Revision cue

Revise wave characteristics through the labels before writing the answer.

Answer writing and exam use

1-mark answer

Wave characteristics are measurable features of a wave, mainly wavelength, frequency, time period, and amplitude.

2-mark answer

Wave characteristics are measurable features of a wave, mainly wavelength, frequency, time period, and amplitude. Frequency f = number of vibrations/time; time period T = 1/f; wavelength λ is distance between consecutive compressions or rarefactions. If a tuning fork vibrates 256 times in one second, its frequency is 256 Hz and its time period is 1/256 s.

3-mark answer

Wavelength is the distance between two consecutive compressions or two consecutive rarefactions. Frequency is the number of vibrations per second, measured in hertz. Time period is the time for one complete vibration. Amplitude is the maximum displacement from the mean position and is linked with loudness. Frequency f = number of vibrations/time; time period T = 1/f; wavelength λ is distance between consecutive compressions or rarefactions. A source completes 240 vibrations in 3 s. Frequency = 240/3 = 80 Hz. Time period = 1/80 s = 0.0125 s. Questions may ask definitions with units, identification from a graph, or simple calculation of frequency and time period. Wrong answer: Frequency is 240 Hz for 240 vibrations in 3 s. This is wrong because the vibrations must be divided by time.
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