Question

Which one of the following scenarios accurately describes a condition in which resonance can occur? A. A column of air has a height equal to 1⁄8 of the wavelength of the sound waves produced by a tuning fork vibrating over the column of air in an open pipe that's partially immersed in water. B. A person is holding a tuning fork on one end of a football field and another person is holding a separate tuning fork on the opposite end of the field. C. A pipe's length is equal to 1⁄2 of the wavelength of the sound waves produced by a tuning fork vibrating over one end of the pipe that's open to the air at both ends. D. A vibrating tuning fork is struck and begins to vibrate as the object used to strike it is placed away from the tuning fork.

Answer 1

The correct option is D.
Resonance is a phenomenon in which a vibrating system or an external force induces another system to vibrate at greater amplitude at particular frequencies. 
When a tuning fork is struck with another object, the tuning fork will start to vibrate as a result of the force that is exerted by the object used to struck it. This type of vibration, without direct excitation by a man is an example of resonance.