Which of the following are not electromagnetic waves?
(i) `alpha`-rays
(ii) Radio waves
(iii) `beta`-rays
(iv) Sound waves
(v) Micro waves
(vi) Cosmic rays

Answer

To determine which of the following are not electromagnetic waves, we will analyze each option based on our understanding of the electromagnetic spectrum.

1. **Understanding Electromagnetic Waves**:
- Electromagnetic waves are waves that propagate through space and do not require a medium. They include radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.

2. **Analyzing Each Option**:
- (i) **Alpha rays**: These are not electromagnetic waves. Alpha rays are composed of helium nuclei (two protons and two neutrons) and are a type of particle radiation.
- (ii) **Radio waves**: These are electromagnetic waves. They are used in communication technologies such as radio and television.
- (iii) **Beta rays**: These are also not electromagnetic waves. Beta rays consist of high-energy, high-speed electrons or positrons emitted by certain types of radioactive nuclei.
- (iv) **Sound waves**: These are not electromagnetic waves. Sound waves are mechanical waves that require a medium (solid, liquid, or gas) to travel through.
- (v) **Microwaves**: These are electromagnetic waves. They are used in microwave ovens and various communication devices.
- (vi) **Cosmic rays**: These are high-energy particles from outer space, primarily protons and atomic nuclei, and are not classified as electromagnetic waves.

3. **Conclusion**:
- The options that are not electromagnetic waves are (i) alpha rays, (iii) beta rays, and (iv) sound waves.

**Final Answer**: The following are not electromagnetic waves: (i) alpha rays, (iii) beta rays, and (iv) sound waves.

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