An observer is timing a runner from a distance of 150 m from the starting block. They start their stopwatch when they see the flash of the starter's pistol instead of when they hear the sound of the gunshot.
What is the main reason for doing this?
The sound of the gunshot takes a significant time to travel 150 m150\text{ m}150 m, whereas light travels almost instantaneously.
Visible light waves can travel through a vacuum, but sound waves cannot.
Human auditory reaction time is significantly slower than visual reaction time.
Sound waves are reflected by nearby objects, creating confusing echoes.
295 exam-style questions on CIE IGCSE Physics Sound, covering Sound. Each one has a worked solution and a mark scheme showing where the marks go.