Visible light is the part of the electromagnetic spectrum the our eyes deserve to see:

It is just a small component of the full spectrum, isn"t it?

Visible Spectrum

Visible Light: the wavelengths that room visible come most human being eyes.

You are watching: Because violet light has more energy than red light,

The key colors, in order, walk "Roy G Bv":Red Orange Yellow Green Blue Violet


As we check out on this beautiful rainbow:




Light has actually a wavelength of around 380 nm to 750 nm, depending upon color.

nm method nanometer, one billionth that a meter.

Example: red light has a wavelength of around 700 billionths the a meter (just much less than one-millionth the a meter). Small!

THz way teraHertz, a trillion cycles per second

So red irradiate vibrates at about 400 million million cycles every second. Fast!

Higher frequency (with shorter wavelength) has more energy:

Red light has actually lower frequency, much longer wavelength and also less energyBlue light has greater frequency, shorter wavelength and an ext energy


Speed the Light

Light travels at virtually 300,000,000 meters every second (to be exact: 299,792,458meters per second) in a vacuum.

That is 300 million meters every second, or:

3 × 108 m/s300,000 km/s186,000 miles every second

At that rate light travels:

1 meterin3.3 ns (3.3 billionths of a second)
Around the Earth"s equatorin134 ms (134 thousandths that a second)
From earth to Moonin1.3 s
Surface of sunlight to Earthinabout 8 minutes

It is for this reason fast, however still takes around 8 minute from the surface ar of the sun to the Earth.

The symbol because that this rate is c:

c ≈ 300,000,000 m/s

Light can Travel Slower

We yes, really shouldn"t call it the speed of light, firstly due to the fact that it applies to the entirety electromagnetic spectrum, and gravity waves, and more. Maybe we could contact it "Max Speed"!

But likewise because irradiate only travel that rate in a vacuum! It deserve to travel slower ...

Wavelengthand Frequency space Linked

The Wavelength and Frequency are related:

Frequency = VelocityWavelength

Wavelength = VelocityFrequency

Assuming the irradiate is ina vacuum, the velocity is the speed of light:3 × 108 m/s

Let"s try a an easy example (in this situation not a wavelength that light):

Imagine a very long wavelength that 75,000 km


Frequency = 300,000 km/s75,000 km

= 4 /s

= 4 Hz

We have the right to fit 4 of those wavelength in 300,000 km, so the vibrates 4 times in 1 second.

So the frequency is 4 Hz (4 every second)

Or, the other way around, if we recognize it vibrates 4 time a 2nd we have the right to calculate that wavelength:

Wavelength = 300,000 km/s4 /s

= 75,000 km

Example: Blue light has actually a wavelength of about 480 nm (480 × 10-9 m)

So the frequency is:

Frequency = 3 × 108 m/s480 × 10-9 m

= 6.25 × 1014 /s

= 6.25 × 1014 Hz

Which is 625 TeraHertz

Light travels in right Lines

Light travels in a right line till its hits something, or it"s path is readjusted by different densities, or through gravity.

Light from the sunlight streams across the road.The shadows likewise show the light travel in right lines.

This irradiate spreads out a little and is scattered by the atmosphere.

Laser beams making straight lines.



Light behaves together a wave, so the can:

scatter (bounce off in every directions),transmit (pass straight through)or obtain absorbed


Light also behaves together packets that energy dubbed Photons.

We have the right to measure a photon"s position and also momentum.Photons have no mass, however each photon has an amount of energy based upon its frequency (number of vibrations per second)Each photon has actually a wavelength

So the is favor a particle and additionally like a wave. This is referred to as the "wave-particle duality".


Einstein wrote:

"It appears as despite we have to use occasionally the one theory and sometimes the other, if at time we may use either."


Intensity is power every area, generally in watts per square meter:

Intensity = W/m2

Example: sun on a small 100 square meter house

About 150 come 300 watts of power are received from the sunlight per square meter.

Let"s choose the smaller number:

Intensity = 150 W/m2

How lot Power is the over the entirety roof?

Power = 150 W/m2 × 100 m2

Power = 15,000 W

So a small house gets around 15 kilowatts top top it"s roof,which is several times much more than a family members uses.

But the is just while the sunlight shines, and only about 20% have the right to be caught by typical solar panels

But the is still lots of power from the Sun.

Inverse Square

Inverse Square: when one worth decreases together the square the the various other value.

Example: light and also distance

The more away we are from a light, the much less bright it is.


The brightness decreases together the square the the distance. Due to the fact that the light is spreading out in every directions:

the energy twice as far away is spread over 4 time the areathe power 3 times as far away is spread over 9 time the areaetc


Light is normally complimentary to vibrate in any type of direction at ideal angles to its path.

But polarized irradiate vibrates in one aircraft only:

Light gets partially polarized once itbounces off surfaces prefer water or glass.

See more: How Many Cm In 22 Inches To Cm, 22 Inches To Cm

Polarizing lenses can block irradiate from the plane, to reduced down on reflected light and also make it much easier to see into water:

Without and with a polarizing lens

Fiber Optics

Light, and also infrared, deserve to be sent out along fiber optic cables, carrying info coded into the wavelength.

Fiber optic cables

The light continues to be inside due to the fact that of a special residential property of refraction: when the refractive table of contents is reduced on the outside, and the edge is not as well steep, the irradiate beam has total internal reflection ~ above the inside:

Light bounces off the walls inside the cable

Fiber optic cables are much much better than electrical wires:

Wires get much more "noise" (other signals that distort or interfere through the original) from strength lines, TV, radio, lightning etc.Photons have no fixed so can swap between 0 and also 1 quickly. Electrons have mass and are slow in comparisonGlass has actually much less resistance come light than copper walk to electrical signals, so can go much further without needing a boost

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Electromagnetic Spectrum Physics Index