Question

Which one of the following is the optical spectral window suitable for remote sensing?

• A. 0.02 – 0.2 μm
• B. 0.4 – 14 μm
• C. 0.8 – 2.0 μm
• D. 0.01 – 1 m

Hint:

For remote sensing, understanding the spectral windows is essential. The optical spectral window spans the visible to infrared regions and is ideal for capturing information about the Earth's surface, vegetation, and temperature.

Answer 1

The Correct Option is B

In remote sensing, the spectral window refers to the range of wavelengths in the electromagnetic spectrum that are useful for capturing data. Different types of sensors are designed to detect specific ranges of wavelengths, and the choice of spectral window affects the quality and type of data that can be captured.
The optical spectral window is crucial in remote sensing because it includes the wavelengths that sensors can detect from Earth’s surface. The window typically used for optical remote sensing lies between the visible and infrared regions, which ranges from approximately 0.4 μm (the violet end of the visible spectrum) to around 14 μm (in the thermal infrared region).
Let's break down the options:
- Option (A) 0.02 – 0.2 μm: This range falls within the ultraviolet region, which is not typically used for general remote sensing because it is absorbed by the atmosphere, particularly by ozone, and it does not provide the most useful data for Earth observation.
- Option (B) 0.4 – 14 μm: This is the correct range for optical remote sensing. It spans the visible light spectrum (approximately 0.4 – 0.7 μm), the near-infrared (0.7 – 1.5 μm), and the thermal infrared (1.5 – 14 μm). Sensors that operate in this range are commonly used in satellite and aerial imaging to capture images of the Earth's surface and atmosphere. This window is ideal for detecting vegetation, land cover, water bodies, and even for thermal imaging to study temperature variations.
- Option (C) 0.8 – 2.0 μm: This range is part of the near-infrared spectrum, often used for vegetation studies and other Earth observation tasks, but it is not the complete optical spectral window.
- Option (D) 0.01 – 1 m: This range includes wavelengths much longer than the infrared region and falls into the microwave and radio wave ranges. It is not suitable for optical remote sensing but is more relevant for radar-based remote sensing.
The correct choice is (B) 0.4 – 14 μm because this range includes the visible, near-infrared, and thermal infrared portions of the electromagnetic spectrum, which are essential for a wide range of remote sensing applications.
Key Concept: Optical remote sensing uses electromagnetic radiation in the 0.4 – 14 μm range, which includes the visible and infrared portions of the spectrum. This range is critical for various applications, including vegetation analysis, temperature mapping, and surface characterization.