WAEC Physics 2018 Paper

Concept:Sound energy is a form of energy, so its S.I. unit is the same as the S.I. unit of all forms of energy.Explanation:Sound waves carry energy from one place to another.In the International System of Units, the unit of energy is the joule, written as $\mathrm{J}$.This applies to every type of energy, including sound, heat, light, and mechanical energy.Let us examine the other options.The hertz ($\mathrm{Hz}$) measures frequency, not energy.The candela ($\mathrm{cd}$) measures luminous intensity.The decibel ($\mathrm{dB}$) measures the loudness or intensity level of sound, not the total sound energy.Since sound energy is energy, its S.I. unit must be the same as that of energy.Hence, the correct unit is the joule.Answer:D. $\mathrm{J}$