[Physics Class Notes] on Visible Light Pdf for Exam

People always see the visible light spectrum, however, some people may be aware of it. In this article, we will get to know about the visible spectrum, wavelength, and colors.

Visible light is that section of electromagnetic waves that is perceivable to human eyes. Anything that glows or produces light has waves of visible light.

The sun, candles, light bulbs, and fire are the things that usually come in people’s minds when they think of light, but visible light is produced from many sources in many different colors.

Some other sources of visible light include television and computer screens, fireworks, and glow sticks.

Visible light forms all the colors of the rainbow. 

Each color has a different frequency and wavelength. When all the colors (i.e., all frequency and wavelength) come together, they form the normal “white” light.

What is the Visible Spectrum?

Visible spectrum is a field of the electromagnetic spectrum that is visible to the human eye. The wavelength of electromagnetic radiation visible to the human eye is called visible light or simply light. Wavelengths of the range of between 380 to 740 nanometers are perceivable to human eyes. Considering the frequency, this corresponds to a band frequency between 405 to 790 THz.

Here, the spectrum doesn’t contain the entire colors, which can be distinguished by the human visual system.

For example, unsaturated colors like pink, or purple variations like magenta are absent because these colors can only be made from a mixture of multiple wavelengths. The colors which contain only one wavelength are called pure colors or spectral colors.

Electromagnetic radiations are transmitted in the form of waves of different wavelengths and frequencies. This broad range of wavelengths of the electromagnetic radiations is called the electromagnetic spectrum.

Electromagnetic spectrum is divided into seven regions in the increasing order of frequency and decreasing order of wavelength. These are radio waves, microwaves, infrared (IR), visible light, ultraviolet (UV), X-rays, and gamma-rays.

The visible light falls between the range of the ultraviolet and infrared regions. The frequency of visible light varies from 4 × 1014 to 8 × 1014 Hz, and the wavelength of visible light varies from 380 nanometers to 740 nanometers.

Spectral Colors

The spectral colors are also called rainbow colors. A spectral color is made up of a single fundamental wavelength on the visible portion of the electromagnetic spectrum, and it’s not composed of a mixture of a number of colours. Spectrals like red, green, orange, and yellow are made up of light waves of a single frequency.

Colors which are produced by visible light of a single wavelength (monochromatic light) are called pure spectral colors. The electromagnetic spectrum is a continuous spectrum with no clear boundaries between one color and the next.

What Does Visible Light do?

The wavelength of light is strong enough to penetrate the retina of the eye and the uppermost dermis in the skin. Humans are capable of perceiving light of wavelength range between 400 nanometers (nm) and 780 nanometers (nm). In fact, there is a gradual transition of wavelengths in the visible part of the spectrum.

Moreover, the eyesight of an individual also varies differently throughout a lifetime due to the aging process of the eye. Significantly, the transparency for short wavelengths of the spectrum, like blue light, decreases with age.

The most important natural source of light for us is the sun. Artificial lights are also very important in our everyday life.

What are Visible Light Examples?

• The sun produces visible light.

• Incandescent light bulbs.

• Neon lights.

• Fluorescent tubes.

• Led bulbs are some other examples of visible light that we use in our day-to-day life.

Visible light is the most important electromagnetic wave for us.

Significance of Light

It is because of light that life is possible on Earth. We do see things only because of light. It also has biological effects; it influences the sleep/wake cycle. It has been used for medicinal and cosmetic proposes for years.

Devices like lasers and IPL function with different wavelengths of lights. For example, light having a high proportion of blue light (or the corresponding wavelength) is used in light therapy devices, daylight lamps to treat “winter depression.” The natural light is used to set the body clock.

Visible lights are essential because, without it, our eyes cannot process images, and we can’t see anything. Apart from sight, there are also many other uses of visible lights. Visible lights are used to make lasers, treat medical surgery, electronic devices like TV, computer, mobile phones and in electric bulbs, etc.

Do You Know?

Sir Isaac Newton divided his color wheel in the following colors, which was: red, orange, yellow, green, blue, indigo, and violet. This order is also said to be “Roy G Biv”, otherwise “VIBGYOR” when taken from the reverse side. In modern divisions of the colors of the spectrum, indigo is often omitted.