Mirage' is a phenomenon due to

Options

A. refraction of light
B. reflection of light
C. total internal reflection of light
D. diffraction of light.

Answer

### Step-by-Step Solution:

1. **Understanding the Conditions for Mirage Formation**:
- A mirage typically occurs on hot summer days or in desert areas. It is essential to recognize that this phenomenon is influenced by temperature gradients in the atmosphere.

2. **Temperature and Density Relationship**:
- On hot days, the ground heats the air directly above it. The air near the ground becomes hotter and thus less dense compared to the cooler air above it. This creates a gradient of air density.

3. **Refractive Index Variation**:
- The refractive index of a medium is inversely related to its density. Therefore, the hotter, less dense air has a lower refractive index compared to the cooler, denser air. This means that the light rays passing through these layers will bend.

4. **Light Refraction and Total Internal Reflection**:
- As light travels from the denser medium (cooler air) to the rarer medium (hotter air), it bends away from the normal. If the angle of incidence exceeds the critical angle, total internal reflection occurs.

5. **Observer's Perception**:
- When an observer looks at the horizon, they see the light that has undergone total internal reflection. This light appears to come from the ground, creating the illusion of a pool of water or a reflective surface, even though there is none.

6. **Conclusion**:
- Therefore, the phenomenon of a mirage is primarily due to the total internal reflection of light caused by the temperature-induced variation in air density.

### Final Answer:
The phenomenon of 'Mirage' is due to **total internal reflection of light**.

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