Greenhouse effect is caused by

Options

A. green plants
B. infrared rays
C. UV rays
D. X-rays

Answer

### Step-by-Step Text Solution

1. **Understanding the Greenhouse Effect**:
The greenhouse effect is a natural process that warms the Earth's surface. When the Sun's energy reaches the Earth, some of it is reflected back to space and the rest is absorbed, warming the planet.

2. **Role of Greenhouse Gases**:
Certain gases in the Earth's atmosphere, known as greenhouse gases (such as carbon dioxide (CO2), methane (CH4), and nitrous oxide (NO2)), trap some of the outgoing infrared radiation. This trapping of heat is what leads to the greenhouse effect.

3. **Impact of the Greenhouse Effect**:
The greenhouse effect is crucial for maintaining the Earth's temperature. Without it, the planet would be too cold to support life. However, an excess of greenhouse gases can lead to global warming, which results in climate change and melting polar ice caps.

4. **Identifying the Cause**:
The question asks what causes the greenhouse effect. The primary cause is the trapping of solar radiation, specifically in the form of infrared rays, by greenhouse gases in the atmosphere.

5. **Evaluating the Options**:
- **Option 1: Green plants** - Incorrect, as they do not cause the greenhouse effect.
- **Option 2: Infrared rays** - Correct, as they are part of the solar radiation that is trapped.
- **Option 3: UV rays** - Incorrect, as they do not contribute to the greenhouse effect.
- **Option 4: X-rays** - Incorrect, as they are not involved in this process.

6. **Conclusion**:
The correct answer to the question "Greenhouse effect is caused by" is **Option 2: Infrared rays**.