Which of the following are based on Tyndall effect?

Options

A. Tail of comets
B. Deltas
C. Blue colour of sky
D. Coagulation

Explanation

To determine which of the given options are based on the Tyndall effect, we need to understand what the Tyndall effect is and analyze each option accordingly.

### Step-by-Step Solution:

1. **Understanding the Tyndall Effect**:
- The Tyndall effect is the scattering of light by colloidal particles in a solution. This scattering makes the path of the light beam visible. It occurs when the particles are larger than the wavelength of light.

2. **Analyzing the Options**:
- **Option A: Tear of Comets**:
- The tails of comets are formed from gas and dust particles that scatter sunlight. As light passes through these particles, it gets scattered, making the tail visible. Therefore, the tear of comets is based on the Tyndall effect.

- **Option B: Dead Tars**:
- Dead tars are not related to the scattering of light in the same way as colloidal solutions. Instead, they are more associated with coagulation, which is a different process. Thus, dead tars do not exhibit the Tyndall effect.

- **Option C: Blue Color of Sky**:
- The blue color of the sky is due to Rayleigh scattering, which is a type of scattering that occurs when light interacts with particles smaller than the wavelength of light. This scattering is similar to the Tyndall effect, as it involves the scattering of light, making the blue color visible. Hence, the blue color of the sky is also based on the Tyndall effect.

- **Option D: Coagulation**:
- Coagulation refers to the process where particles clump together and is not related to the scattering of light. Therefore, coagulation does not exhibit the Tyndall effect.

3. **Conclusion**:
- Based on the analysis, the options that are based on the Tyndall effect are:
- **A: Tear of Comets**
- **C: Blue Color of Sky**

### Final Answer:
The correct options based on the Tyndall effect are **A (Tear of Comets)** and **C (Blue Color of Sky)**.

---