Question

A ringing bell is sending a longitudinal wave to your ear. What else is true about the longitudinal wave? Check all that apply.

All sound waves are longitudinal.
Energy is transferred perpendicular to the wave’s motion.
Mechanical waves can be longitudinal.
Electromagnetic waves can be longitudinal.
Longitudinal waves require a medium to travel through.

Answer 1

Answers:
- All sound waves are longitudinal. — False. In fluids (air, water) sound is longitudinal, but in solids sound can also have transverse (shear) modes.
- Energy is transferred perpendicular to the wave’s motion. — False. That is true for transverse waves. In a longitudinal wave the particles and the energy transfer are along (parallel to) the direction of propagation.
- Mechanical waves can be longitudinal. — True. Sound waves in air are an example of mechanical longitudinal waves.
- Electromagnetic waves can be longitudinal. — False (for free-space radiation). EM waves in free space are transverse. (Longitudinal EM components can appear in special situations like waveguides or plasmas.)
- Longitudinal waves require a medium to travel through. — True (for ordinary longitudinal waves like sound): they are mechanical disturbances and need a material medium to propagate.