To solve the question "Which of the following does not contain material particles?", we will analyze each option provided in the question.
### Step-by-Step Solution:
1. **Understanding Alpha Rays**:
- Alpha rays consist of alpha particles, which are essentially helium nuclei.
- An alpha particle has a mass number of 4 and an atomic number of 2 (represented as \( \alpha \, ^4_2 \)).
- Since alpha particles have mass and charge, they are considered material particles.
**Hint**: Recall that material particles have mass and charge.
2. **Understanding Beta Rays**:
- Beta rays consist of beta particles, which are electrons or positrons.
- A beta particle is represented as \( \beta \, ^{-1}_0 \) for electrons, indicating a negatively charged particle.
- Like alpha particles, beta particles also have mass and charge, making them material particles.
**Hint**: Identify the charge and mass of beta particles to conclude they are material.
3. **Understanding Gamma Rays**:
- Gamma rays are electromagnetic radiation of high energy.
- Unlike alpha and beta particles, gamma rays do not consist of material particles; they are just energy waves with no mass and no charge.
**Hint**: Differentiate between particles and waves; gamma rays are waves.
4. **Understanding Canal Rays (Anode Rays)**:
- Canal rays consist of positively charged particles (often protons or other ions).
- They are produced in a discharge tube and also have mass and charge, qualifying them as material particles.
**Hint**: Remember that charged particles, regardless of being positive or negative, are considered material.
5. **Conclusion**:
- From the analysis, we see that alpha rays, beta rays, and canal rays all consist of material particles.
- Gamma rays, however, do not contain any material particles as they are purely energy.
Thus, the correct answer to the question is **gamma rays** (option 3), as they do not contain material particles.
### Summary of the Answer:
The option that does not contain material particles is **gamma rays**.
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