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The light that human beings can see is called visible light . Visible light is actually just a small part of the large spectrum of electromagnetic radiation which you will learn more about in [link] . We can think of electromagnetic radiation and visible light as transverse waves. We know that transverse waves can be described by their amplitude, frequency (or wavelength) and velocity. The velocity of a wave is given by the product of its frequency and wavelength:

v = f × λ

However, electromagnetic radiation, including visible light, is special because, no matter what the frequency, it all moves at a constant velocity (in vacuum) which is known as the speed of light. The speed of light has the symbol c and is:

c = 3 × 10 8 m . s - 1

Since the speed of light is c , we can then say:

c = f × λ

Colour and light

Our eyes are sensitive to visible light over a range of wavelengths from 390 nm to 780 nm (1 nm = 1 × 10 - 9 m). The different colours of light we see are related to specific frequencies (and wavelengths ) of visible light. The wavelengths and frequencies are listed in [link] .

Colours, wavelengths and frequencies of light in the visible spectrum.
Colour Wavelength range (nm) Frequency range (Hz)
violet 390 - 455 769 - 659 × 10 12
blue 455 - 492 659 - 610 × 10 12
green 492 - 577 610 - 520 × 10 12
yellow 577 - 597 520 - 503 × 10 12
orange 597 - 622 503 - 482 × 10 12
red 622 - 780 482 - 385 × 10 12

You can see from [link] that violet light has the shortest wavelengths and highest frequencies while red light has the longest wavelengths and lowest frequencies .

A streetlight emits light with a wavelength of 520 nm.

  1. What colour is the light? (Use [link] to determine the colour)
  2. What is the frequency of the light?
  1. We need to determine the colour and frequency of light with a wavelength of λ = 520 nm = 520 × 10 - 9 m.

  2. We see from [link] that light with wavelengths between 492 - 577 nm is green. 520 nm falls into this range, therefore the colour of the light is green.

  3. We know that

    c = f × λ

    We know c and we are given that λ = 520 × 10 - 9 m. So we can substitute in these values and solve for the frequency f . ( NOTE: Don't forget to always change units into S.I. units! 1 nm = 1 × 10 - 9 m.)

    f = c λ = 3 × 10 8 520 × 10 - 9 = 577 × 10 12 Hz

    The frequency of the green light is 577 × 10 12 Hz

A streetlight also emits light with a frequency of 490 × 10 12 Hz.

  1. What colour is the light? (Use [link] to determine the colour)
  2. What is the wavelength of the light?
  1. We need to find the colour and wavelength of light which has a frequency of 490 × 10 12 Hz and which is emitted by the streetlight.

  2. We can see from [link] that orange light has frequencies between 503 - 482 × 10 12 Hz. The light from the streetlight has f = 490 × 10 12 Hz which fits into this range. Therefore the light must be orange in colour.

  3. We know that

    c = f × λ

    We know c = 3 × 10 8 m . s - 1 and we are given that f = 490 × 10 12 Hz. So we can substitute in these values and solve for the wavelength λ .

    λ = c f = 3 × 10 8 490 × 10 12 = 6 . 122 × 10 - 7 m = 612 × 10 - 9 m = 612 nm

    Therefore the orange light has a wavelength of 612 nm.

Questions & Answers

I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
How can I make nanorobot?
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Maths test. OpenStax CNX. Feb 09, 2011 Download for free at http://cnx.org/content/col11236/1.2
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