Vibrations give rise to sound. When an object vibrates, it compels the nearby particles of the medium to vibrate, causing a disturbance in the medium. This disturbance then propagates as waves, reaching the ear and giving rise to the sensation of sound.
(i) The kind of person the doctor is (money, possessions)
(ii) The kind of person he wants to be (appearance, ambition)
∆ABC is an isosceles triangle in which AB = AC. Side BA is produced to D such that AD = AB (see Fig. 7.34). Show that ∠ BCD is a right angle.

Sound is a vibration that propagates the mechanical wave of displacement and pressure, through a medium can be of any matter. In other words, the sound is the thin line between Music sound and Noise.
Sound can be divided into two types depending on its frequency. The following are:-