Why do some wavelengths of light get blocked by Earth’s atmosphere?

Earth’s atmosphere blocks certain wavelengths of light primarily because of the way gases and particles within it interact with electromagnetic radiation. The atmosphere is made up of various gases like nitrogen, oxygen, water vapor, and trace gases, which absorb and scatter different wavelengths of light.

Here’s a breakdown of why specific wavelengths are blocked:

1. Ozone Layer (UV Light): The ozone layer, located about 10 to 30 miles above Earth’s surface, absorbs most of the Sun’s harmful ultraviolet (UV) radiation. The ozone molecules are very effective at absorbing UV light, especially in the range of 200 to 300 nanometers, which protects life on Earth from harmful effects like skin cancer.
2. Water Vapor (Infrared): Water vapor in the atmosphere absorbs infrared radiation, especially in the wavelength range between 1 and 10 micrometers. This is why infrared radiation doesn’t easily pass through the atmosphere. It’s also why the Earth’s surface is warmer than it would otherwise be without the greenhouse effect, as water vapor traps heat in the atmosphere.
3. Carbon Dioxide (Infrared): Like water vapor, carbon dioxide (CO2) also absorbs infrared light, but it absorbs in different wavelength ranges. This contributes to the greenhouse effect, trapping heat and warming the Earth.
4. Rayleigh Scattering (Visible Light): Visible light is largely unaffected by absorption in the atmosphere, but some scattering occurs, particularly at shorter wavelengths (blue and violet). This scattering by molecules like nitrogen and oxygen is why the sky appears blue during the day.
5. Clouds and Aerosols (Various Wavelengths): Clouds, dust, and other particles in the atmosphere can scatter and absorb light in a wide range of wavelengths. For instance, clouds can block visible light, reducing sunlight that reaches the Earth’s surface.

So, the atmosphere acts as a filter, allowing some wavelengths of light to pass through (such as visible light) while blocking or absorbing others (like UV and most infrared). This helps regulate the amount of solar energy that reaches Earth’s surface and also protects life from harmful radiation.