________also serve a useful purpose in solar cookers, as they reflect sunlight into the cooker helping to cook food faster.

Options

A. Periscopes
B. Kaleidoscope
C. Spherical mirror
D. Plane mirrors

Answer

To solve the question, we need to identify what reflects sunlight in solar cookers to help cook food faster.

### Step-by-Step Solution:

1. **Understanding Solar Cookers**: Solar cookers are devices that utilize sunlight to cook food. They are designed to capture and concentrate sunlight to generate heat.

2. **Role of Reflection**: In solar cookers, the sunlight needs to be directed towards the cooking area where the food is placed. This is achieved through reflection.

3. **Identifying the Reflective Surface**: The reflective surface used in solar cookers is crucial for directing sunlight. The most effective type of mirror for this purpose is one that can reflect sunlight efficiently into the cooking area.

4. **Types of Mirrors**: There are different types of mirrors, such as plane mirrors, spherical mirrors, and others. Among these, we need to determine which one is best suited for reflecting sunlight in solar cookers.

5. **Conclusion**: The answer is a **plane mirror**. Plane mirrors are flat and can reflect light uniformly, making them ideal for directing sunlight into the cooking area of the solar cooker.

### Final Answer:
**Plane mirrors** also serve a useful purpose in solar cookers, as they reflect sunlight into the cooker helping to cook food faster.

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