Dear Milad Fallah ,

The interaction between material and light is dictated by the energy band diagram or structure of the material. To be photons to be absorbed by the material:

- The wave length of the incident light must be eqaul or less the critical wavelength corresponding to the energy gap such that Eg= hc/lambda critical.

- The other condition is that the thickness of the path must be

greater equal to 1/alpha where alpha is the absorption coefficient.

I would like to pay your attention that the gas molecules can absorb light provided that the incident photons has the proper photon energy.

It is observed as the wavelength decreases alpha increases. So, normally shorter wavelengths needs less thickness of material to be absorbed.

Best wishes

@ Milad, may be due to surface plasmon resonance. Oscillating electric fields of a light ray propagating near a colloidal nanoparticle interact with the free electrons causing a concerted oscillation of electron charge that is in resonance with the frequency of visible light.

Dear Milad Fallah ,

The interaction between material and light is dictated by the energy band diagram or structure of the material. To be photons to be absorbed by the material:

- The wave length of the incident light must be eqaul or less the critical wavelength corresponding to the energy gap such that Eg= hc/lambda critical.

- The other condition is that the thickness of the path must be

greater equal to 1/alpha where alpha is the absorption coefficient.

I would like to pay your attention that the gas molecules can absorb light provided that the incident photons has the proper photon energy.

It is observed as the wavelength decreases alpha increases. So, normally shorter wavelengths needs less thickness of material to be absorbed.

Best wishes

Dear Prof. Tarafdar, and Prof. Zekry,

Thank you so much for your response and time.