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Every material on earth shows its own strength of reflection in each wavelength when it is exposed to the electromagnetic waves (visible light and invisible light, such as infrared rays, ultraviolet rays or electric waves). Also, when the material gets hot, it radiates showing its own strength in each wavelength.
The figure below shows the strength of reflection and radiation from plants, earth and water in each wavelength. The horizontal axis shows wavelength, left side is shorter and right side is longer. According to wavelength, it is called as ultraviolet ray, visible light, infrared ray, microwave, etc.
Strength of reflection and radiation of electromagnetic
waves from plants, earth and water in each wavelength.
Also, the strength of reflection and radiation differs according to the condition of objects, such as type of plants, status (dead, weak, etc.) or contamination of water. For example, the figure below shows the difference of reflectance by the status of plant, from the top, leafy heALT = hy plants, dry feeble plants, and dead plants.
Difference of reflectance according to the condition of plants
Sensors aboard the earth observation satellites are capable to acquire the strength of reflection and radiation in each wavelength. From the observation data, we can understand the status of forests, ocean pollution and desertification. |
