

Explanation
(a)(i) Resonance is a phenomenon which occurs whenever a body is set in oscillation at its own natural frequency as a result of impulses received from another vibrating body, vibrating with the same frequency.
(ii) Examples of resonance are:
(1) Loud sound from vibrating prongs of a tuning fork.
(2) Bridge vibrating under uniform matching of soldiers.
(3) Repeated jumping of a diver at the free end of a diving board causes the board to resonate.
(4) Rattling of car engine at high speed causing vibrating of the body of the car. (5) X\(_{c}\) equals X\(_L\) in an L-C-R series circuit for tuning a radio set.
(iii)




Loudness


Intensity




- The magnitude of the sensation resulting from sound reaching the ear.
-Sensation that depends on the individual hearing ability.


- The time rate of flow of energy per unit area perpendicular to the direction of propagation of the sound.
- Depends on physical quantities of energy, time and area





(b) The following properties will change in speed and wavelength.

(c)


(d) \(\frac{1}{u} + \frac{1}{v} = \frac{1}{f}\)
\(\frac{1}{v} = \frac{1}{f} - \frac{1}{u} = \frac{1}{-18} - \frac{1}{90}\)
= \(\frac{-5 -1}{90}\)
v = -15m
M = \(\frac{u}{v} = \frac{h_i}{h_o}\)
\(h_o = \frac{hi \times u}{v} = \frac{1 \times 90}{1.5}\)
= 6.0 m

