Visible Light

Visible light waves is a form of electromagnetic radio waves including infrared radiation, X-rays, microwaves and ultraviolet radiation. Visible light is usually defined as the wavelength that are visible to most of the human eyes. We can see these waves as the colors of the rainbow where each color includes a different wavelength. Red has the longest wavelength and violet has the shortest one. When all the waves are seen together, they form a white light. When white light comes through the prism, it gets broken into the colors of the visible light spectrum.

Visible Light

EM radiation can be transmitted in waves or particles at different frequencies and wavelengths. This wide variety of wavelengths is known as the electromagnetic spectrum. It is divided into seven areas in decreasing order of wavelength and increasing order of energy and frequency.

Visible light comes under the range of EM spectrum between infrared and ultraviolet having a frequency of about 4 x 10 14 to 8 x 10 14 cycles per second and wavelengths of about 740 nanometers or 2.9 x10 -5 inches to 380nm.

Visible Light


The most important characteristics of visible light is color which is both an inherent property of light and an artifact of the human eye. Our eyes include specialized cells known as cones. These cones acts as a receivers that is tuned to the wavelength of the narrow band of the EM spectrum. Light at the lower end of the visible spectrum has a longer wavelength of about 740 nm. It is seen as red, green in the middle and violet at the upper end of the spectrum having a wavelength of about 380 nm.

Color and Temperature

As the object gets hotter with the temperature, they radiate energy which is dominated by shorter wavelengths by changing its color before our eyes. For instance, a blow torch turns bluish from reddish as it is adjusted to burn hotter. The sun produces yellow light than any other color as its surface temperature  is 5,500°C. If the sun’s surface is cooler, 3,000°C then it would look reddish. If the Sun is hot , 12,000°C then it would look blue.

Practise This Question

An object moves such that it is at a constant length from a given point. The motion of the object can be:

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