What is light? What is refraction?Why do sun rays have a warming effect?

What is light?

The sun warms our planet,and the Earth releases a huge spectrum of radiation in the universe.The light is a only a small part of spectrum,namely,the visible portion of the spectrum-colours of the rainbow.We do not perceive other forms of radiation such as ratio waves or microwaves.Light rays can travel through vacuum in the universe,but when they fall on the matter,they get refracted.This phenomenon of refraction is used in instruments such as lenses or glasses for people with weak eyesight.

Why do sun rays have a warming effect?

Our body perceives a part of the wavelengths radiated out by the sun as heat.This portion is known as infrared radiation and includes the wavelengths larger than those of the visible light.Using this knowledge, we make infrared lamps,which are used in medicine to relax muscular tensions with their soothing warmth.We can perceive other wavelengths of the solar radiation such as ultraviolet(UV)radiation too,but indirectly.The UV rays have shorter wavelengths,so they have more energy.They can penetrate into our body cells and destroy them.They can also cause skin cancer.Therefore,we should always protect ourselves against these harmful radiations of the sun by wearing protective clothing or by using sunscreens.

What is refraction?

Light penetrates into different transparent materials at different speeds.A beam of light coming from the air,for instance,changes its speed when it falls on the surface of the sea and enters water- it becomes slower.As a result,the light waves moves in a different direction and it gets deflected or refracted.The phenomenon of the change in direction of the light wave due to change in its speed is called refraction.