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1800-102-2727Commonly referred to as visible light for less ambiguity, light is the electromagnetic radiation that is part of the electromagnetic spectrum, which can be perceived by the human eye. Visible light has wavelengths in the range of 400 - 700 nanometers (nm) and frequency values between 430 and 750 terahertz (THz). Visible light is characterized by properties like intensity, propagation direction, frequency or wavelength spectrum and polarization. All types of electromagnetic radiation, including light, has a speed of 299,792,458 meters per second (m/s) in the vacuum. This value of light, often denoted by the letter ‘c’, is a fundamental constant in physics and related fields. It is extremely important to mention ‘visible’ when addressing light waves that are perceivable by the human eye because, in physics, the term light refers to any electromagnetic radiation of any wavelength like for example, gamma rays, X-rays, microwaves and radio waves are also light, even if the light waves are visible or not. Light demonstrates both particle and wave characteristics, and this is referred to as the dual nature of light or also called the wave-particle duality. As is the case with any electromagnetic radiation, light propagates through free space in the form of waves, but on impact with the target or any obstacle, it imparts energy as particles do; the energy is absorbed in single locations. This energy imparted is in the form of photons, and this represents the quanta of light. The study of light is known as optics.
Wavelength is defined as the measured distance between two identical points on two successive waves. Wavelength can be measured either between two successive crests or two successive troughs. Light propagates through free space in the form of transverse waves; the direction of motion of the wave is perpendicular to the direction of oscillation of the photons. Wavelength is represented by the symbol λ (lambda), and the units are nanometers (nm) or micrometers (µm). The wavelength, in the case of waves, can be expressed as follows.
Or in the case of particles as
where
Visible light comprises multiple different wavelengths, and each wavelength corresponds to a different color. The color of objects humans perceive is a result of the reflection of light waves by that object. The molecules of an object absorb all other wavelengths of light except one, which is then reflected by it and perceived by the human eye in color specific to that wavelength. The sun, which is the primary source of light for our planet, produces polychromatic light. That is, the light waves from the sun are considered to be white, which is the combination of all the seven visible light spectrum colors. However, in the case of lasers, the light produced will be one specific color, and is called monochromatic because the color of the light depends on the wavelength. The seven colors of the visible spectrum are violet, indigo, blue, green, yellow, orange and red.
Color | Wavelength (in nm) | Frequency (in THz) |
White | 750 - 400 | 790 - 400 |
Red | 750 - 610 | 480 - 405 |
Orange | 610 - 590 | 510 - 480 |
Yellow | 590 - 570 | 530 - 510 |
Green | 570 - 500 | 580 - 530 |
Blue | 500 - 450 | 670 - 580 |
Indigo | 450 - 425 | 600 - 670 |
Violet | 425 - 400 | 700 - 790 |