Question

Decibel is the unit of physical quantity used for:
A. The speed of light
B. The intensity of heat
C. The intensity of sound
D. The frequency of radio waves

Answer 1

Hint: The decibel (dB) is a logarithmic unit of measurement that expresses the ratio of two quantities having the same units, on logarithmic scale. The ratio may be of quantities such power or field quantities.

Complete step by step answer:
The decibel (dB) is commonly used to quantify sound levels, it is the unit of sound pressure level.

The decibel is a logarithmic unit that indicates the ratio of a physical quantity to a reference level. It is one tenth of a bel, which was named after the inventor of the telephone, Alexander Graham Bell.

The word decibel comes from the prefix ‘deci’ that is one tenth of the word it precedes. Which means one decibel is one tenth of a bel.

Although the decibel can be used to talk about a number of different quantities such as the power, voltage, sound pressure and intensity etc.

Generally, we express the intensity of sound in decibel units.

Hence, the correct option is C, i.e., The intensity of sound.

Additional Information:
One decibel (0.1 bel) equals 10 times the common logarithm of the power ratio. In mathematical expression, the intensity of a sound in decibels is, \[10{{\log }_{10}}\dfrac{{{S}_{1}}}{{{S}_{2}}}\].

Where, \[{{S}_{1}}\] and \[{{S}_{2}}\] are the intensities of two sounds, i.e., doubling the intensity of a sound means an increase of 3 dB approximately.

Note: Students should understand the physical significance of a decibel and they should also keep in mind that the decibel is a logarithmic ratio of the quantities such as sound pressure, power, voltage, and intensity etc.