$(a)$ $A$ mobile ringing inside a vacuum chamber cannot be heard outside. Why?
$(b)$ Represent a transverse wave graphically.
$(c)$ What is meant by loudness of sound? On what factor does it depend?

(N/A) Sound is a mechanical wave and requires a material medium (like air,water,or steel) to propagate. Since a vacuum chamber contains no particles to transmit the vibrations of the sound wave,the sound cannot travel from the mobile to the outside.
$(b)$ $A$ transverse wave is represented by a sinusoidal graph showing crests (points of maximum positive displacement) and troughs (points of maximum negative displacement) along the direction of propagation.
$(c)$ Loudness is a physiological measure of the response of the ear to the intensity of sound. It depends primarily on the amplitude of the vibrating particles of the medium. The greater the amplitude,the louder the sound.