Electromagnetic waves propagate in a vacuum. Consider the following statements:
- I. The electric and magnetic fields oscillate perpendicular to each other.
- II. Electromagnetic waves require a material medium to propagate.
- III. Electromagnetic waves carry energy and momentum.
Which of these are correct?
- AI and II
- BII and III
- CI and III
- DAll
Show answer and explanation
Correct answer: (c) I and III
Explanation
- I is correct: in an electromagnetic wave, the electric and magnetic fields oscillate perpendicular to each other and to the direction of travel. So these are transverse waves.
- II is wrong: electromagnetic waves need no medium. They travel through a vacuum at about 3 × 10⁸ m/s. That is how sunlight reaches the Earth.
- III is correct: they carry energy and momentum. The momentum shows up as radiation pressure, which, for example, pushes comet tails away from the Sun.