When a source of sound is moving in air with the speed faster than the speed of sound, the shape ofthe wave front produced would be a,(1) plane (2) sphere (3) cylinder (4) cone (5) parabola
This phenomenon is called the sonic boom. It happens when an object travels faster than the velocity of sound.
When an object travels, it creates a series of pressure waves in front and behind the object. When it travels faster than the velocity of sound this waves merge with each other and travels at the speed of sound. The wavefront create at this stage is an advancing wave front which has the look of a Cone.
Since the object will travels faster than the sound an stationary observer will here the sound of the object few seconds after it passed him.
So the answer is a cone shape wave front.
The correct one is (4)