Which of the following is/are false regarding cathode rays?

Options

A. They possess kinetic energy
B. They are electromagnetic waves
C. They produce heat
D. They produce mechanical pressure

Explanation

To determine which statements regarding cathode rays are false, we will analyze each statement based on the properties of cathode rays.

### Step-by-Step Solution:

1. **Understanding Cathode Rays**:
- Cathode rays are streams of electrons that are emitted from the cathode (negative electrode) in a vacuum tube when a high voltage is applied.

2. **Statement Analysis**:
- **Statement 1**: "Cathode rays have kinetic energy."
- **Analysis**: True. Cathode rays consist of electrons that are accelerated towards the anode, which gives them kinetic energy.

- **Statement 2**: "They are electromagnetic waves."
- **Analysis**: False. Cathode rays are not electromagnetic waves; they are composed of charged particles (electrons). Electromagnetic waves, such as light, do not consist of charged particles.

- **Statement 3**: "They produce heat."
- **Analysis**: True. When cathode rays collide with the walls of the discharge tube, they transfer energy, which can produce heat.

- **Statement 4**: "They produce mechanical pressure."
- **Analysis**: True. The impact of cathode rays on surfaces can exert pressure, as the momentum of the electrons transfers to the surface they collide with.

3. **Conclusion**:
- The only false statement regarding cathode rays is that they are electromagnetic waves (Statement 2).

### Final Answer:
The false statement regarding cathode rays is: **They are electromagnetic waves.**

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