Weight of the light

Light is something which makes object visible. Light is so common that we hardly wait and wonder what its made of. Here are some facts about Light.

Rays of light at Chicago union center (1943) | Wikimedia Commons

Light is simply the electromagnetic wave falling under certain range of frequency which our eyes have learned to sense and differentiate with colours. A typical human eye will respond to wavelengths from about 390 to 700 nm. In terms of frequency, this corresponds to a band in the vicinity of 430–790 THz. Also light is the fastest moving object in whole universe. (Atleast, until we find something more faster than light) Light does not require and medium to travel, though is speed is affected by the medium.

Light exhibits properties that both of particle as well as wave. Light shows Doppler effect just like sound wave, which results in red shift and blue shift. The light of object moving towards you at considerable higher speed will appear blue (Blueshift) and when it is moving away from you, it will appear red (Redshift). This is how we came to know that the nearest Galaxy Andromeda is moving towards us. Also Light is affected gravity just like particles!

Doppler effect on Light illustration | Wikimedia commons

Light has weight though negligible, it has. It isn't rest mass though. In fact all forms of energy has weight. Light weighs more than the empty box. If we could measure something as large as Metro City, it will weigh 100 Kg more in Day than it will at night. It is because of weight of light has momentum and exerts pressure on it. Also, spaceship may be pushed as much as 1000 miles from its destination say Mars, because of Light pushing it. This phenomena is called Light Pressure.

Light is affected by gravity. The velocity of light in vacuum is 299 792 458 m/s. Gravity affects the path of light the same way as matter, but the result is too insignificant to be seen. The effect can be observed on something which is very huge and very far away from the observer, for example distant object in space like cluster of stars or galaxy. Another example which proves that light is affected by gravity is Black hole. It is said that the Gravity of Black hole is so strong that even light cannot escape it.

Refraction | Wikimedia Commons

Refraction is caused by sudden change in speed of light when it changes the medium. Also, due to refraction the path of light may get diverted Prism uses refraction to form spectrum of colours. Lens also work on same principle to magnify the image of the object.
Other examples are Formation of mirage, appearance of sky as bluish and the pencil or pen dipped in glass of water appears broken.

Prism forming Light spectrum | Wikimedia Commons

So in short, Light is awesome!Physics is Awesome and so is Science and the whole Universe!