Light -An Introduction

1. Light is an electromagnetic radiation, which gives rise to a sensation of sight.

2. Light has the following properties: –

(i) We see objects when light falls on it and is reflected our eyes.

(ii) The speed of light is same when measured from any direction and is equal to 3 × 108 ms-1 in vacuum. The speed of all colours of light is equal.

(iii) White light consists of seven colours VIOLET, INDIGO, BLUE, YELLOW, GREEN, ORANGE, and RED [VIBYGOR]. It’s also called the spectrum of light.

(iv) The spectrum of light consists of infra-red, visible and ultraviolet.

(v) An astronomical distance between stars, galaxies or planets is measured in Light years. One light year is the distance traveled by Light in one year.

(vi) Light can travel in the vacuum.

(vii) All electromagnetic radiations are not light.

(viii) The unit of light is called a photon.

(ix) Red light has the largest wavelength among visible light. Therefore, it travels the longest. Traffic lights are red so that it can be visible for long distance.

(x) Edward Hubble noticed that the starlight colour is slowly shifting towards the RED end of the spectrum. This led him to predict Universe is expanding.

(xi) Persons with colour blindness cannot detect certain colours of light.

(xii) The speed of light changes when it travels from one medium to a second medium. For example, from Air to water or from Air to Glass or from Water to Glass.

(xiii) Reflection, Refraction, Dispersion, Diffraction, Interference, and Polarisation are some of the important phenomena exhibited by Light.

(xiv) Light travels in straight line.

(xv) Light can be both a particle and a wave. This is called duality of light and is the starting concept of Quantum Physics.

Light is fundamental to modern Physics.

Here is a compendium of information in PDF  Notes on Light.

Check out the complete list of TOPICS in the ‘LIST’

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