Transparency

Transparency

This animation explains transparency and opacity, the principle of radiography, and the light-absorbing properties of materials.

Physics

Keywords

transparency, color filter, color absorption, opacity, absorption, color, glass, X-ray film, X-radiation, X-ray, photon, light, particle, wave, ray of light, filter, quantum mechanics, quantum physics, quantum, atom, physics

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Scenes

  • - It is excited by the absorbed photon: an electron in it jumps to a higher energy state. When the electron jumps back to the ground state, it releases a photon, the color of which is the same as that of the absorbed photon.

Color filters

  • - It absorbs red color, therefore only the blue and green components of white light can pass through the filter. The mixture of blue and green light gives cyan color.
  • - It absorbs blue color, therefore only the red and green components of white light can pass through the filter. The mixture of red and green light gives yellow color.

Certain materials absorb or transmit light of different wavelengths (that is, of different color) to a different extent. These materials can serve as color filters and modify the color of a light beam. Let's consider, for example, a material that absorbs blue light, while it lets red and green light pass through. If we illuminate this material by white light, it produces yellow light.

Color filters - micro level

  • - It is excited by the absorbed photon. The atoms of the filter cannot be excited by photons of any color: the atoms of the yellow filter only absorb the photons of blue light.
  • - It is excited by the absorbed photon. The atoms of the filter cannot be excited by photons of any color: the atoms of the cyan filter can only absorbs the photons of red light.

Color filters - atomic level

  • - It is excited by the absorbed photon. The atoms of the filter cannot be excited by photons of any color: the atoms of the yellow filter only absorbs the photons of blue light.
  • - It is excited by the absorbed photon. The atoms of the filter cannot be excited by photons of any color: the atoms of the cyan filter can only absorb the photons of red light.

  • - It absorbs red color, therefore only the blue and green components of white light can pass through the filter. The mixture of blue and green light gives cyan color.
  • - It absorbs blue color, therefore only the red and green components of white light can pass through the filter. The mixture of red and green light gives yellow color.
  • - It is excited by the absorbed photon. The atoms of the filter cannot be excited by photons of any color: the atoms of the yellow filter only absorb the photons of blue light.

Narration

Transparent objects let light pass through them, while opaque objects absorb it. To explain this phenomenon, we must understand how the particles of light, photons are absorbed.

The atoms and molecules in materials are capable of absorbing photons. The absorbed photon excites the particles; an electron in the atom jumps to a higher energy state. When the electron releases a photon of the same wavelength as the absorbed photon, it jumps back to the ground state. The released photon then excites another atom, and the process goes on. That is, photons are trapped inside opaque materials.

Particles cannot be excited by photons of any color. Certain atoms and molecules can absorb photons of several colors, so materials composed of such particles are opaque. The particles in transparent materials, however, do not absorb light, they allow photons to pass through them.

If a material only absorbs photons of a certain color while allowing photons of other colors to pass through, the light that passes though the material will have a different color. This phenomenon is used in color filters. For example, if a material absorbs blue light but allows red and green light to pass through, it will produce yellow light when it is illuminated by white light.

Like visible light, X-radiation is a form of electromagnetic radiation. Its wavelength, however, is much shorter. Some of the tissues in the human body are transparent for X-rays, while others, bone tissue, for example, absorb X-radiation. This phenomenon makes it possible to create images of the internal structure of the body with X-ray machines.

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