Which of the following statements-about electromagnetic waves is not correct?

Step 1: Analyze the question We need the statement that is NOT correct about electromagnetic (EM) waves.

Step 2: Key concept EM waves (radio waves, light, X-rays, gamma rays, etc.) are made of oscillating electric and magnetic fields. These fields:

• are perpendicular to each other,
• are both perpendicular to the direction the wave travels.

This makes EM waves transverse, not longitudinal.

Step 3: Check each option

• A. They carry energy as they travel through space. Correct. Sunlight carries energy to Earth.
• B. They travel with the speed of light. Correct. In a vacuum, all EM waves travel at c = 3.0 × 10⁸ m/s.
• C. They are longitudinal. Not correct. EM waves are transverse. Longitudinal waves, such as sound, need a medium and have vibrations along the direction of travel.
• D. The electric and magnetic fields are at right angles to each other. Correct. This is the standard description of an EM wave.

Step 4: Answer

Tip: Remember "EM = Transverse". Light can be polarised, and only transverse waves can be polarised. Also remember that sound is longitudinal and needs a medium, whereas EM waves can travel through a vacuum.