The Electromagnetic Spectrum - Visible Light

What is a Visible Light?

Visible light has wavelengths of around 400 nm to 700 nm and a frequency range of around 400 THz to 800 THz. This is the part of the electromagnetic spectrum that can be “seen” and distinguished optically by the human eye. When white light is passed through the prism it spreads into the seven colours of the visible light spectrum. The Sun is an example of a natural visible light source.

Visible Light

Although we are blind to many wavelengths of light (which may be visible to some animals), we have instruments in place to detect them. But our world is oriented entirely around visible light as we can perceive it easily.

Apart from the most obvious use for visible light (we use it to see), certain properties of light (like not being able to pass through solid walls, artificial lighting) make us extremely dependable on them. Nowadays we can use visible light as a means of communicating. Visible Light Communication (VLC) can be used as a means of mobile connection (with a certain amount of disregard for security) and for communication in areas like hospitals where Wi-Fi and mobile phones are undesirable.

What is a Visible Light Spectrum?

The segment of the electromagnetic spectrum that human eyes can see is known as the visible light spectrum. Moreover, this range of wavelengths is called visible light. Typically, human eyes can detect wavelengths from 380 nanometres to 700 nanometres.

How do we see using Visible Light?

The sun is a natural source of visible light waves. Everything we see is the reflection of this sunlight off the surrounding objects.  Cones in our eyes are the receivers of these tiny light waves. The colour of the object that we see is the colour of the light that is reflected off the object. All the other colour are absorbed.

Visible Light Astronomy

The temperature of hot objects such as stars can be estimated using their temperatures. For example, the sun’ surface temperature is 5,800 Kelvin. The sunlight has a peak wavelength of about 550 nm, which we perceive as visible white light. If the sun’s temperature were cooler, about  3,000 C it would look reddish. If it were hotter, about 12,000 C, it would look blue.

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