# A report onLight and Wavelength

Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 terahertz, between the infrared (with longer wavelengths) and the ultraviolet (with shorter wavelengths).

- Light

Examples of waves are sound waves, light, water waves and periodic electrical signals in a conductor.

- Wavelength

## Electromagnetic spectrum

The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies.

This frequency range is divided into separate bands, and the electromagnetic waves within each frequency band are called by different names; beginning at the low frequency (long wavelength) end of the spectrum these are: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays at the high-frequency (short wavelength) end.

In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic (EM) field, propagating through space, carrying electromagnetic radiant energy.

In physics, electromagnetic radiation (EMR) consists of waves of the electromagnetic (EM) field, propagating through space, carrying electromagnetic radiant energy.

It includes radio waves, microwaves, infrared, (visible) light, ultraviolet, X-rays, and gamma rays.

The position of an electromagnetic wave within the electromagnetic spectrum can be characterized by either its frequency of oscillation or its wavelength.

## Visible spectrum

Portion of the electromagnetic spectrum that is visible to the human eye.

Portion of the electromagnetic spectrum that is visible to the human eye.

Electromagnetic radiation in this range of wavelengths is called visible light or simply light.

## Frequency

Number of occurrences of a repeating event per unit of time.

Number of occurrences of a repeating event per unit of time.

Frequency is an important parameter used in science and engineering to specify the temporal rate of change observed in oscillatory and periodic phenomena, such as mechanical vibrations, audio signals (sound), radio waves, and light.

For periodic waves in nondispersive media (that is, media in which the wave speed is independent of frequency), frequency has an inverse relationship to the wavelength, λ (lambda).

## Refraction

Redirection of a wave as it passes from one medium to another.

Redirection of a wave as it passes from one medium to another.

Refraction of light is the most commonly observed phenomenon, but other waves such as sound waves and water waves also experience refraction.

The refractive index of materials varies with the wavelength of light, and thus the angle of the refraction also varies correspondingly.

## Spectrum

Condition that is not limited to a specific set of values but can vary, without gaps, across a continuum.

Condition that is not limited to a specific set of values but can vary, without gaps, across a continuum.

The word was first used scientifically in optics to describe the rainbow of colors in visible light after passing through a prism.

Soon the term referred to a plot of light intensity or power as a function of frequency or wavelength, also known as a spectral density plot.

## Hertz

Unit of frequency in the International System of Units (SI) and is defined as one cycle per second.

Unit of frequency in the International System of Units (SI) and is defined as one cycle per second.

Light is electromagnetic radiation that is even higher in frequency, and has frequencies in the range of tens (infrared) to thousands (ultraviolet) of terahertz.

(For historical reasons, the frequencies of light and higher frequency electromagnetic radiation are more commonly specified in terms of their wavelengths or photon energies: for a more detailed treatment of this and the above frequency ranges, see electromagnetic spectrum.)

## Refractive index

In optics, the refractive index ( refraction index) of an optical medium is a dimensionless number that gives the indication of the light bending ability of that medium.

The refractive index can be seen as the factor by which the speed and the wavelength of the radiation are reduced with respect to their vacuum values: the speed of light in a medium is v = c/n, and similarly the wavelength in that medium is λ = λ0/n, where λ0 is the wavelength of that light in vacuum.

## Telescope

Optical instrument using lenses, curved mirrors, or a combination of both to observe distant objects, or various devices used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation.

Optical instrument using lenses, curved mirrors, or a combination of both to observe distant objects, or various devices used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation.

Optical telescopes, using visible light

The dishes are sometimes constructed of a conductive wire mesh whose openings are smaller than the wavelength being observed.