What is Light and Heat ?

What is Light and Heat ?

What is refraction ?

Light travels in straight lines. However, when it travels from one medium to another, for examples, from air to water, it bends. Bending of light at the boundary of the two media is known as refraction. It occurs because the speed of light changes as it enters a different medium.

How does a lens work ?

A lens is a carefully moulded piece of transparent material, such as glass or plastic, which refracts light to form an image.

When we look through a lens, we observed that the image of an object gets distorted. It's because light undergoes refraction as it travels from air to glass, and back to air again.

Lenses are usually used to magnify or reduce the size of the images of object. they are used :

Magnifying glasses

microscopes

spectacles

cameras

telescopes

Dispersion of light through a prism

We can prove this by shining white light through a prism. A prism is a transparent plastic or glass object, with smooth flat sides, that can refract light.

White light is refracted twice as it passes through a prism once, when it travels from air to the prism, and a second time when it travels from the prism to air. Light that comes out of the prism is no longer white, but it is broken up into the colours of rainbow. The breaking up of white light into its component colours is known as dispersion.

Dispersion occurs because of light of different colours travel at different speeds. Red light travels the fastest so, it refracts the least. Violet light travels the slowest so, it refracts the most. That is why red is always seen at one end of the rainbow, and violet at the other end.

Dispersion of light through water droplets

Water droplets in the air can act as tiny prisms. The droplets can be from the rain, the mist of a waterfall or a fine spray of water from a garden hose. It refract the sunlight the same way a prism does, and produce rainbows.

Transfer of heat

As light travels from one medium to another, heat also travels from one object or place to another. Heat travels from a region of higher temperatures to a region of lower temperature through conduction, convection and radiation.

Conduction

Heat can transfer transfer from one part to another within an object between objects.

An object is heated up, its particles collide with one another. Heat is transferred from the hotter region to the cooler region through these collisions of particles.

Conduction also occur between objects. Heat transferred when particles of both objects are touching each other.

Convection

Transfer of heat from one region to another by the movement of fluids is know as convection. 

A fluid is heated up, it expands. This means that its volume increases an its density decreases.

Hotter less dense fluid then rises and floats. Cooler, denser fluid flows to take its place. 

Radiation

Radiation release heat from the surface of most bodies that transferred  directly from one region to another.

Heat directly transferred without having to travel through any substance. Means that heat can be transferred without air.

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