Interaction Between Radiation and the Material

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Interaction Between Radiation and the Material. Prof. Arnon Karnieli The Remote Sensing Laboratory Jacob Blaustein Institute for Desert Research Ben-Gurion University of the Negev Sede-Boker Campus 84990, ISRAEL. Radiation Interaction with a Matter. Transmission.

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Interaction Between Radiation and the Material

Prof. Arnon Karnieli

The Remote Sensing Laboratory

Jacob Blaustein Institute for Desert Research

Ben-Gurion University of the Negev

Sede-Boker Campus 84990, ISRAEL

Transmission
• Incident radiation passes through the material without attenuation
• Change in the direction of radiation is given by the index of refraction of the material
Refraction and Diffraction

Transmitted waves are refracted or diffracted:

Refraction occurs when an electromagnetic wave crosses a boundary from one medium to another. A wave entering a medium at an angle will change direction.

Diffraction refers to the "bending of waves around an edge" of an object. Diffraction depends on the size of the object relative to the wavelength of the wave.

Index of Refraction

1

2

Index of refraction (n) is the ratio of the speed of light in vacuum relative to the speed of light through the material

Snell’s law describes refraction angles:

Absorption

- The material is opaque to incident radiation

- A portion of EMR is converted to heat (re-radiated)

Reflection

Reflectance

- Diffuse reflection (rough surface)

- Specular reflectance (smooth surface)

Scattering

(DIFFUSE)

Atmosphere Effect on Satellite Image

With atmosphere

No atmosphere

Atmospheric Gases

Nitrogen (N2) - 78%, Oxygen (O2) - 21%, Carbon Dioxide (CO2) - 0.03 %, plus other miscellaneous gases (e.g., H2O).

Rules - 1

Rules govern the interaction between energy and the atmospheric media:

1. Since there is an indirect relationship between the energy of the photon and the wavelength, less electronic influence on the atmospheric particles is expecting in long wavelengths.

Ep= h*c/ 

Rules - 2

2. The longer the wavelength, the lesser statistical probability for a contact between the radiation and the atmospheric particles.

Scattering

Scattering: random re-direction of the radiation ray from parallel orbit to to an omni-direction orbit.

ScatteringTypes

Scattering Types

1. Selective scattering

- Rayleigh scattering

- Mie scattering

2. Non-selective scattering

Selective: Rayleigh Scattering

Partical size << 

Type of particles: gases, atmospheric molecules

Scattering intensity

Mostly affects blue light

UV/Skylight Filter

No Filter

Skylight Filter

Selective: Mie Scattering

to

Partical size  

Mean diameter 0.1 to 10m

Type of particles: dust, smoke, soot, volcanic ash, water vapor, polen

Scattering intensity

Mostly affects red light

Mie Scattering – Air Pollution

Haifa, Israel, November 2004

Mie Scattering – Volcanic Eruption

Mt. Pinatubo stratospheric Aerosol layer as seen from Space Shuttle STS-43 (August 1991). The stratospheric aerosol layer forming two distinct strata is clearly visible approximately 10 kilometers above the cloud tops.

Mie Scattering – Haze Episode