WAEC Physics 2015 Theory — Question 15

Model answer

(i) Resonance is the phenomenon of forced vibration in which a system is set into vibration at its own natural frequency as a result of impulses or forced vibrations received from an external vibrating body/source of the same frequency. (ii) Examples: (a) reception of radio programmes from a distant transmitting station; (b) the production of sound from musical instruments; (c) oscillation of the air in a bottle caused by a vibrating tuning fork; (d) a pendulum bob forcing another pendulum of the same length to oscillate. (iii) Intensity of a sound wave is an objective, measurable physical quantity - the rate of sound energy flow per unit area. Loudness is the subjective sensation experienced by a listener, which depends mainly on the amplitude of the sound wave but also on the listener's sensitivity; the same intensity may be perceived as differently loud by different listeners.