Question

Which of the following are not electromagnetic waves?

• A. Cosmic ray
• B. X-ray
• C. $\beta$-ray
• D. $\alpha$-ray

Hint:

Remember: - EM waves: X-rays, $\gamma$-rays, visible light - Particle radiations: $\alpha$, $\beta$, cosmic rays (mostly particles)

Answer 1

The Correct Option is C

Concept: Electromagnetic (EM) waves are waves that do not require a medium and consist of oscillating electric and magnetic fields. Examples include X-rays, gamma rays, etc. However, some radiations are actually particle radiations:
• $\alpha$-rays: Helium nuclei ($2p + 2n$)
• $\beta$-rays: Fast-moving electrons or positrons

Step 1: Analyze each option.

• Cosmic rays → High-energy particles (mostly protons), not purely EM waves
• X-rays → Electromagnetic waves
• $\beta$-rays → Particles (electrons), not EM waves
• $\alpha$-rays → Particles (helium nuclei), not EM waves

Step 2: Identify correct choices.
The radiations which are not electromagnetic are: \[ \beta\text{-rays and } \alpha\text{-rays} \]

Step 3: Final conclusion.
Thus, the correct answer is: \[ (C) and (D) \]