Question

The earth’s atmospheric window is in the
a. Ultraviolet region
b. Visible region
c. Infrared region
d. Polar region

Answer 1

Hint: Any of the wavelengths at which electromagnetic radiation from space can penetrate the earth's atmosphere is called the atmospheric window. Some of the major atmospheric windows include the visible window ranging from approximately $0.3$ to $0.9\mu m$; approx. $8$ to $13\mu m$ ranging the infrared window and at wavelengths longer than about $1mm$ falls under the microwave window.

Complete answer:
• There are generally two atmospheric windows. Electromagnetic radiation such as infrared, ultraviolet, X-ray, and gamma-ray wavelengths are generally absorbed by the Earth's atmosphere.
• So, the radio and visible wavebands are suitable for ground-based astronomy.
• The atmospheric window is present in the part of the spectrum from the areas where there are no clouds generally present.
• Originating near the earth's surface, some of the infrared radiation leaves the atmosphere and are transmitted relatively unimpeded through the atmosphere.
• The absorption of the greenhouse gases is almost $100\% $ efficient in the region of infrared wavelengths.
• But there is a window between $8$ and $13mm$, near the peak of terrestrial emission, where the atmosphere is only a weak absorber of ozone gas at 9.6 mm. This is why ozone acts as a strong greenhouse gas.
• The detailed composition of our atmosphere is an important practical consequence of the interaction of electromagnetic radiation with matter.
• Only through the regions of atmospheric windows, certain wavelength regions can penetrate the atmosphere.
• These wavelengths generally fall under the region of infrared and not generally visible or ultraviolet.
• Also, the polar region is not included under the spectrum of light.

Hence, the correct answer is option (C).

Note: Between $8$ and $13\mu m$, the troposphere is transparent to terrestrial radiation. The atmospheric window is closed by clouds which absorb outgoing radiation and reradiating much of this energy back to Earth's surface. Wavelengths that occur within atmospheric windows range where the atmosphere is transparent. Remote sensing projects must be conducted. Outside of these windows, there is simply no radiation from the sun to detect i.e. the atmosphere has blocked it.