Windows

In the electromagnetic spectrum, a window is a range of wavelengths that can pass through a material or atmosphere relatively easily.

Earth's atmosphere does not transmit all electromagnetic wavelengths equally. Some regions pass through well, while others are strongly absorbed. Important examples include: Visible window — much visible light reaches Earth's surface. Radio window — many radio frequencies can pass through the atmosphere.

Atmospheric windows are important in: astronomy; communication; * remote sensing. For example, some telescopes can operate from Earth's surface because the atmosphere is transparent in those wavelength ranges. Other wavelengths may require satellites or high-altitude instruments.