Question

Define:

(1) Wavelength

(2) Frequency

(3) Amplitude

(4) Echo

Answer 1

(1) Wavelength (λ)

The distance between two consecutive compressions or rarefactions of a sound wave is called its wavelength (λ). Equivalently, it is defined as the distance between two consecutive crests or troughs of a transverse wave.

The SI unit of wavelength is metre (m).

Distances BF or DH represents the wavelength of the given wave.

(2) Frequency (ν)

The number of cycles/vibrations produced by a source of sound per second is called frequency. It only depends on the source.

If five crests of a wave pass through a fixed point in one second, then it is said that the frequency of the wave is 5 cycles per second.

Pitch of the sound is directly proportional to its frequency.

The SI unit of frequency is Hertz (Hz).

(3) Amplitude (A)

Amplitude of a wave is the maximum displacement of medium particles in either direction from their equilibrium (rest) position. The transverse equivalent of a longitudinal sound wave is shown in the following figure:

The medium particles have displaced to maximum heights of MP, ER, or IT and maximum depths of QC or SG. These heights/depths are called the amplitudes of the wave i.e., MP = ER = IT = QC = SG = amplitude of the wave. The SI unit of amplitude is metre (m).

The loudness of a sound is directly related to its amplitude. A loud sound has larger amplitude as compared to a soft sound.

(4) Echo:

It is repetition of sound due to reflection of original sound from any hard surface. For example, when you clap in a big hall, you first hear the original sound and then the reflected sound. This reflected sound is the echo of the original sound.