Q hc A h V

Where

Q is the energy of quantum, h = Planck's constant

Shefali Aggarwal

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Table 2: Principal Divisions of the Electromagnetic Spectrum

Wavelength

Description

Gamma rays

Gamma rays

X-rays

X-rays

Ultraviolet (UV) region 0.30 |lm - 0.38 |m (1|lm = 10-6m)

This region is beyond the violet portion of the visible wavelength, and hence its name. Some earth's surface material primarily rocks and minerals emit visible UV radiation. However UV radiation is largely scattered by earth's atmosphere and hence not used in field of remote sensing.

Visible Spectrum 0.4 | m - 0.7 | m Violet 0.4 | m -0.446 | m Blue 0.446 | m -0.5 | m Green 0.5 | m - 0.578 | m Yellow 0.578 |m - 0.592 |lm Orange 0.592 |m - 0.62 |m Red 0.62 |m -0.7 |m

This is the light, which our eyes can detect. This is the only portion of the spectrum that can be associated with the concept of color. Blue Green and Red are the three primary colors of the visible spectrum. They are defined as such because no single primary color can be created from the other two, but all other colors can be formed by combining the three in various proportions. The color of an object is defined by the color of the light it reflects.

Infrared (IR) Spectrum 0.7 |m - 100 |m

Wavelengths longer than the red portion of the visible spectrum are designated as the infrared spectrum. British Astronomer William Herschel discovered this in 1800. The infrared region can be divided into two categories based on their radiation properties.

Reflected IR (.7 |m - 3.0 |lm) is used for remote sensing. Thermal IR (3 | m - 35 | m) is the radiation emitted from earth's surface in the form of heat and used for remote sensing.

Microwave Region 1 mm - 1 m

This is the longest wavelength used in remote sensing. The shortest wavelengths in this range have properties similar to thermal infrared region. The main advantage of this spectrum is its ability to penetrate through clouds.

Radio Waves (>1 m)

This is the longest portion of the spectrum mostly used for commercial broadcast and meteorology.

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