An example of a mechanical wave is---------

Step 1: Analyze the question The question asks which option is a mechanical wave.

Step 2: Explain the concept

• A mechanical wave needs a material medium (solid, liquid, or gas) to travel. It transfers energy by making the particles of the medium vibrate. Examples: sound waves, water waves, waves on a string, seismic waves.
• An electromagnetic wave does not need a medium. It can travel through a vacuum, such as the space between the Sun and the Earth. Examples: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, gamma rays.

Step 3: Check each option

• A. Water waves: These travel through water, and the water particles vibrate as the wave passes. They need a medium, so they are mechanical.
• B. Radio waves: These are part of the electromagnetic spectrum and need no medium, so they are not mechanical.
• C. X-rays: These are high-frequency electromagnetic waves, so they are not mechanical.
• D. Light rays: Light is electromagnetic and travels through a vacuum, so it is not mechanical.

Step 4: Answer The correct option is A. water waves.

Exam tip: Ask yourself, "Can it travel through empty space?" If yes, it is electromagnetic. If no, it is mechanical. Remember that all the waves in the electromagnetic spectrum (radio, microwave, infrared, light, UV, X-ray, gamma) are not mechanical. Sound is the other mechanical wave that often appears in WASSCE questions.