visible light

(noun)

the part of the electromagnetic spectrum, between infrared and ultraviolet, that is visible to the human eye

Related Terms

Examples of visible light in the following topics:

  • Visible Light

    • Visible light is the portion of the electromagnetic spectrum that is visible to the human eye, ranging from roughly 390 to 750 nm.
    • Visible light, as called the visible spectrum, is the portion of the electromagnetic spectrum that is visible to (can be detected by) the human eye.
    • Visible light is produced by vibrations and rotations of atoms and molecules, as well as by electronic transitions within atoms and molecules.
    • Colors that can be produced by visible light of a narrow band of wavelengths (monochromaticlight) are called pure spectral colors.
    • This allows visible light to heat the surface.

  • Infrared Waves

    • Infrared (IR) light is EM radiation with wavelengths longer than those of visible light from 0.74 µm to 1 mm (300 GHz to 1 THz).
    • Infrared (IR) light is electromagnetic radiation with longer wavelengths than those of visible light, extending from the nominal red edge of the visible spectrum at 0.74 micrometers (µm) to 1 mm.
    • Near-infrared, from 120 to 400 THz (2,500 to 750 nm) - Physical processes that are relevant for this range are similar to those for visible light.
    • Infrared light from the Sun only accounts for 49% of the heating of the Earth, with the rest being caused by visible light that is absorbed then re-radiated at longer wavelengths.
    • Visible light or ultraviolet-emitting lasers can char paper and incandescently hot objects emit visible radiation.

  • Ultraviolet Light

    • Ultraviolet (UV) light is electromagnetic radiation with a wavelength shorter than that of visible light in the range 10 nm to 400 nm.
    • Ultraviolet (UV) light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, that is, in the range 10 nm to 400 nm, corresponding to photon energies from 3 eV to 124 eV (1 eV = 1.6e-19 J; EM radiation with frequencies higher than those of visible light are often expressed in terms of energy rather than frequency).
    • UV light is found in sunlight (where it constitutes about 10% of the energy in vacuum) and is emitted by electric arcs and specialized lights such as black lights.
    • This is a plot of Earth's atmospheric opacity (opposite of transmittance) to various wavelengths of electromagnetic radiation, including visible light.
    • Visible light passes relatively unimpeded through the atmosphere in the "optical window."

  • Electron Microscopes

    • The amount of light which passes through the target depends on its densities, since the less dense regions allow more light to pass through than the denser regions.
    • This is because their de Broglie wavelengths are so much smaller than that of visible light.
    • You hopefully remember that light is diffracted by objects which are separated by a distance of about the same size as the wavelength of the light.
    • Therefore, the sizes at which diffraction occurs for a beam of electrons is much smaller than those for visible light.
    • This is why you can magnify targets to a much higher order of magnification using electrons rather than visible light.

  • Fluorescence and Phosphorescence

    • Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation.
    • In most cases, the emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation.
    • Fluorescence occurs when an orbital electron of a molecule or atom relaxes to its ground state by emitting a photon of light after being excited to a higher quantum state by some type of energy.
    • The most striking examples of fluorescence occur when the absorbed radiation is in the ultraviolet region of the spectrum, and thus invisible to the human eye, and the emitted light is in the visible region .
    • Commonly seen examples of phosphorescent materials are the glow-in-the-dark toys, paint, and clock dials that glow for some time after being charged with a bright light such as in any normal reading or room light .

  • Diffraction

    • Diffraction occurs with all waves, including sound waves, water waves, and electromagnetic waves such as visible light, X-rays and radio waves.
    • The most striking examples of diffraction are those involving light.
    • Diffraction in the atmosphere by small particles can cause a bright ring to be visible around a bright light source like the sun or the moon.
    • A shadow of a solid object, using light from a compact source, shows small fringes near its edges.
    • All these effects are a consequence of the fact that light propagates as a wave.

  • Dispersion of the Visible Spectrum

    • Within the electromagnetic spectrum, there is only a portion that is visible to the human eye.
    • Visible light is the range of wavelengths of electromagnetic radiation that humans can see.
    • When a light ray enters a medium with a different index of refraction, the light is dispersed, as shown in with a prism.
    • When white light enters the prism, it spreads.
    • (b) White light is dispersed by the prism (shown exaggerated).

  • The Speed of Light

    • But what exactly is the speed of light?
    • It is just that: the speed of a photon or light particle.
    • where v = actual velocity of light moving through the medium, c = speed of light in a vacuum, and n = refractive index of medium.
    • The refractive index of air is about 1.0003, and from this equation we can find that the speed of visible light in air is about 90 km/s slower than c.
    • As mentioned earlier, the speed of light (usually of light in a vacuum) is used in many areas of physics.

  • Scattering of Light by the Atmosphere

    • The particles that scatter the light also need to have a refractive index close to 1.
    • This law applies to all electromagnetic radiation, but in this atom we are going to focus specifically on why the atmosphere scatters the visible spectrum of electromagnetic waves, also known as visible light.
    • As we just learned, light scattering is inversely proportional to the fourth power of the light wavelength.
    • This is why the sun appears to be a light yellow color.
    • The remaining unscattered light is of longer wavelengths and so appears orange.

  • Dispersion: Rainbows and Prisims

    • These colors are associated with different wavelengths of light.
    • White light, in particular, is a fairly uniform mixture of all visible wavelengths.
    • Sunlight, considered to be white, actually appears to be a bit yellow because of its mixture of wavelengths, but it does contain all visible wavelengths.
    • Thus violet light is bent more than red light and the light is dispersed into the same sequence of wavelengths .
    • (b) White light is dispersed by the prism (shown exaggerated).