IB Physics Higher Level (HL) Practice Exam

The greenhouse effect primarily arises from the trapping of infrared radiation by atmospheric gases, which are commonly referred to as greenhouse gases. These gases, such as carbon dioxide, methane, and water vapor, absorb thermal energy emitted from the Earth's surface. When sunlight reaches Earth, a portion of it is absorbed, warming the planet. The Earth then radiates this energy back into space in the form of infrared radiation. However, greenhouse gases in the atmosphere absorb some of this outgoing infrared radiation, preventing it from escaping and thereby warming the atmosphere further. This process is fundamentally important for maintaining the Earth's temperature at a level that supports life. Without the greenhouse effect, the planet would be significantly colder, making it less hospitable. Therefore, the capture and re-radiation of infrared energy by greenhouse gases is the primary mechanism that drives the greenhouse effect, leading to an increase in global temperatures.