Free Worksheets, Lessons, Quizzes
Free Worksheets, Lessons, Quizzes
What is light? Light is an electromagnetic wave made up of little packets of energy called photons.
Light is indispensable in our life. Without light we cannot imagine life on Earth. Our day-to-day activities would be inefficient and life would probably be boring in a world without light. So, we cannot take light lightly. Here, in this lesson we’re going to talk all about light.
What time of the day do you see things clearly? Day time or night time? Yes, it is the day time that you can get a clear vision of everything you see, because at night it is dark everywhere unless you turn the lights on or use a torch.
During the day time you see things very well thanks to the sunlight. The sun is the main source of light on earth.
What is Electromagnetic Spectrum? Read the lesson to know about it.
Without light from the sun, the world would be in darkness. At night we have to use an artificial source of light such as light bulbs, torches, electric lamps, candlelight etc. to get a clear vision of the things we see.
This indicates that we need to use some kind of a source of light to see. Without light we are unable to see, even though with eyes wide open.
You are reading this article now. You have enough of light to read it.
Now close your eyes.
Are you still reading this article? Or don’t have a clue what’s in the next line.
You wouldn’t be able to read this question, if you’ve actually closed your eyes. So, now probably you’ve opened your eyes back. Why? This is because you couldn’t see anything that you’re reading.
So, what does this indicate? Is only light enough to see things? No. We also need our eyes to see things. Here, eyes means, proper eyesight. People who are blind also have a pair of eyes, but they cannot see, because they don’t have their eyesight. People who are with poor eyesight need to wear a pair of spectacles or contact lenses to see things better.
Therefore, we need both light and proper eyesight to see things clearly.
What are the factors essential to see things better?
Light is an electromagnetic wave. It is the smallest quantity of energy that can be transported.
Light is made up of little packets of energy. We call these Photons.
A photon is an elementary particle which represents a quantum of light or other electromagnetic radiation.
A photon doesn’t have a real size.
A photon cannot be split. It can only be created or destroyed.
We know light is radiated by a source of light, such as the Sun, light bulb, candle, torch etc. We also call these luminous sources.
(Click to read the lesson sources of light)
So, how do luminous sources radiate light?
When the atoms of a luminous source get heated up, it ‘excites’ the electrons of the atoms and gain extra energy. This extra energy is released as a photon. If the source of light gets hotter and hotter, it releases more photons. This is how luminous sources radiate light.
Example:
The energy comes from electricity to the light bulb. It heats the light bulb. This heat ‘excites’ the electrons of the atoms by gaining extra energy, which is released as photons, and the light bulb gives off light.
Energy conversion in a light bulb
Next, let’s see how can light be an electromagnetic wave.
Electromagnetic spectrum is the enormous range of wave lengths and frequencies over which electromagnetic radiation extends.
Visible light is only a tiny part of electromagnetic spectrum.
So, visible light is a type of energy in form of electromagnetic radiation.
Electromagnetic radiation consists of enormous range of wave lengths and frequencies, such as gamma rays, UV rays, visible light, radio waves etc.
Components of Electromagnetic Spectrum
Electromagnetic Spectrum
A ray is the direction of the path in which light is travelling.
A ray is represented in diagrams by a straight line with an arrow on it.
A Light Ray
A beam is a stream of light.
It is shown by a number of rays and can be three types: parallel, diverging (spreading out) or converging (getting narrower).
A Light Beam
Different types of beams of light
Have you seen sunbeams streaming through trees early in the morning or light from a cinema projector on its way to the screen? If the answer is yes, then you have seen how light travels in straight lines. These beams are visible, since the dust particles in the air reflect light into our eyes.
Sunbeams streaming through clouds
Sunbeams streaming through clouds
Sunbeams streaming through clouds
Sunbeams streaming through trees
Sunbeams streaming through trees
Sunbeams streaming through trees
Light is essential for plants to make food through the process, ‘photosynthesis’.
Without light we cannot get a clear vision of anything that we see.
Illumination is done during festive seasons, for advertising purposes etc. using colourful light bulbs.
Colour lights give messages to drivers and pedestrians like when to stop, get ready and move. Road signs are non-incandescent objects which glow in the dark. (Click to read the lesson sources of light).
Laser light sources work differently than the normal sources of light.
In laser light sources the excited atoms act together and emit a narrow, very bright beam of light.
The first laser was invented in 1960.
Laser Light
Laser is used vastly in the field of medicine, industry, and agriculture. Read the following list of uses of laser in today’s world.
Laser is used in;