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Facts About Light - The Basics
The Speed Of Light
Light is a form of energy and it is considered to exist as a wave. Defined at times as a beam of particles called photons, light is one of nature's greatest gifts to all living beings as it enables vision.
Discussing light as energy, waves, and photons simply goes beyond the basics. So let us discuss only the very basics of light right here.
Light travels in a straight line, and there is a speed associated with light. This is known as the speed of light.
What is the speed of light? Well, The speed of light is 186284 miles per second. That means, for every second light covers a distance of 186284 miles. This distance is equivalent to six journeys around the earth.
Light traveling in a straight line, passes through certain substances. Whatever prevents light from passing through, is known to be opaque, whereas what permits light to pass through is called transparent.
Materials which allow light to pass through but with some distortion are called translucent substances. Although light passes through them, the distortion prevents identifying objects that are viewed through such materials.
Frosted glass and tissue paper are some examples of translucent substances.
Sunlight - Light From The Sun
Light from the sun takes 8 minutes and 32 seconds to reach the earth. At the speed of 186284 miles per second, the distance travelled in 8 minutes and 32 seconds would be approximately 93,000,000 miles, which is the distance between the sun and the earth.
Nature has imposed certain limitations on speeds such that nothing can travel faster than the speed of light.
Let There Be A Flash Of Light!
Moonlight? No Way!
A luminous substance is a substance that glows, and emits light of its own. A luminous body is a body that emits light of its own.
The moon is not a luminous body and does not emit light of its own. We see the moon all lit up only when the light of the sun falls on it.
Therefore there is no such thing as moonlight! Light from the moon is actually sunlight that is reflected from the surface the moon.
Although poets and songwriters knew this all along they went on and wrote songs and verses revolving around moonlight! How deceptive!
A Lunar Eclipse
When the earth is exactly between the sun and the moon, we witness what is called a total lunar eclipse. This is because the earth getting in between the sun and the moon blocks the light from the sun from falling on the moon.
What we see is the shadow of the earth falling on the moon completely covering it in the case of a total lunar eclipse.
However, the paths of orbit of the earth and the moon are such that this event is very rare indeed.
A Solar Eclipse
A solar eclipse occurs when the moon gets in between the earth and the sun, blocking the sunlight from the earth. In this case, the shadow of the moon falls on the earth. Often we witness a partial solar eclipse.
Still On The Basics - Incandescence
Light is generated when a substance is heated to a very high temperature.
This occurs in the filament of an incandescent bulb. Here, the filament, through which a current passes, offers resistance to the current flow and the resistance thus offered generates intense heat, causing it to glow white hot.
The term "heated to incandescence" means a substance is heated until it turns white hot. Usually this is done in the absence of air.
The Use Of Light In Analyzing Substances
Analyzing certain substances require that they be heated to incandescence.
The light emitted by a substance when heated to that state reveal a lot about the substance concerned.
Always this is done in the absence of air. I shall discuss this more in a later hub.
Let There Be Light!
What Is A Light Year?
On the subject of light, and the enormous speed at which it travels, imagine if you could travel at the speed of light continuously for one whole day, how far do you think you will go?
If the period of time is one whole month ... or lets make it one year. Okay, if you travelled for one full year continuously at the speed of light, without stopping anywhere at all, the distance you would have covered would be 5874652224000 miles. So that figure is one light year in miles.
To say it simply, one light year is actually the distance travelled if you travel at the speed of light for one full year. So 5874652224000 miles is one light year. [186284 x 365 x 24 x 60 x 60].
Another way of saying it is, one light year is something in excess of five thousand eight hundred and seventy four billion miles! [something more than 5874 billion miles]
In other words, one light year is the physical distance covered, by travelling continuously at the speed of light for one full year. So, a light year is actually a term used to describe this enormous distance. Lets go !!!
What Is Velocity Of Light?
Well, velocity and speed are the same in terms of displacement or distance covered within a specified period of time, and could be explained without straying from the basics.
The word velocity indicates that the object that is associated with a particular speed has a definite direction.
In this case, since light travels in a straight line, there is a definite direction involved.
Even if the object in question traverses a circle like a spacecraft orbiting the earth, then the displacement of the spacecraft can be referred to as velocity.
The criterion here is, if the velocity of a body is known, its exact location could be predicted at any given time in the future, whereas knowing only the speed of an object nobody but GOD would be able to predict where the hell that object would be after a certain period of time has elapsed.
So now you understand what velocity of light actually means.
In A Lighter Vein!
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Do you know where we are heading for? If you are now reading this in English, it won't be long before you wouldn't! Would you consider a hundred years a long period of time?
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More Facts About Light - Einstein And The Speed Of Light
The involvement of the speed of light in the theory of relativity is one of the most interesting features in science.
Having a proper understanding of the very basics is essential to go deeper into this most fascinating field.
The speed of light does not follow any acceptable form of logic. It's consistency is irrespective of the speed of it's source.
Here is an example to illustrate this phenomenon.
Someone running at a speed of twenty miles per hour, hurls a stone at a target which is located straight ahead, relative to the runner.
If the speed at which the stone is thrown is forty miles per hour, then the stone will strike its target at a speed of sixty miles per hour, which is the sum total of the speeds of both bodies.
The sum total of the speeds of both bodies means the speed of the runner added to the speed at which the runner throws the stone. This will appear most logical to you.
Well everything in science is, especially when you understand the very basics clearly.
Conversely, while you are traveling at a speed of twenty miles per hour in vehicle, if you throw a stone at an object at a speed of forty miles per hour, directly behind you, in exactly the direction which is opposite to your actual motion, then the speed at which the stone strikes the object will be the original speed at which you threw it, reduced by the speed of the vehicle.
In the case of light, this does not happen. Why? Well watch the videos on this page, which will initiate you into developing an interest in this most fascinating topic.
Read more about the nature of light here. This article goes a little beyond the basics. However it is written in simple English and is easy to understand.
Discover more interesting things about the way light behaves and more about light itself. This could be just the beginning of a long voyage for you ... a long one, from which you could even emerge as the very next EINSTEIN.
My best wishes to you, Einstein Jr!
Tell Us What You Know
What do you know about light?
Light - The Fundamentals Of Its Speed
- The Speed Of Light
Here is the link to Wikipedia's page on light.
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