Posted
on February 28, 2016
I
like referring to him as “C.V.” because his full name is
Chandrasekhara Venkata Raman. Which is a lot to type.
On
the other hand, like Charles Darwin and Albert Einstein, at least
spell check know's Raman's full name and didn't allow me to
accidentally type something like Chardrasekhara or Chandrasakhara
or....whatever else my flying fingers blundered out.
And
since 1929, Raman's full name ALSO included “Sir,” because he was
knighted by Britain.
So,
why am I bringing up Sir Chandrasekhara Venkata Raman today? Just
because he was an Indian scientist and today is National Science Day
in India?
Actually,
it is because of Raman that today was chosen to celebrate and promote
science in India – because today is the anniversary of his most
important, Nobel-Prize-worthy discovery: the Raman effect.
So...what's
the Raman effect?
You
probably know that visible light is a form of electromagnetic
radiation, along with infrared, microwaves, X-rays, radio waves, and
ultra-violet light. All electromagnetic radiation travels in little
“packets” called photons.
I
bet you have heard that, on a clear day, the sky looks blue because
of scattering. But what is being scattered by what?
Air
is not empty space – it's full of lots of different particles and
molecules, most of which are invisible to us. When light from the Sun
hits particles or molecules, some of the photons's paths are
disrupted, and the various photons scatter about randomly. And blue
photons have the tiniest wavelengths of all visible light, so they
tend to get scattered more than green or yellow photons, and
especially more than orange or red photons.
This
is called Raleigh scattering, or elastic scattering. The photons that
scatter shoot off on other, random paths, but they don't change their
frequency and wavelength. In other words, a photon of blue light
stays a photon of blue light.
In
1923, a physicist predicted that a few photons would scatter in
another way. They would scatter by excitation – in other words,
they would change frequency and wavelength, either gaining or losing
energy. A photon of blue light might become a photon of red, or vice
versa.
On
this date in 1928, Raman and K. S. Krishnan discovered the predicted
behavior. Only about one photon in 10 million changes wavelength as
it scatters, but they were able to observe it as light passed through
a liquid.
(Actually,
two Soviet scientists discovered this same sort of scattering as
light traveled through crystals about a week before Raman and
Krishnan's discovery! The reason that the “effect” is named after
Raman – and the reason that Raman and Krishnan share a Nobel Prize
for the discovery – is that the Indian scientists published their
findings before the Russian scientists did.)
In
1928, the Raman effect seemed important to scientists, especially
those in the field of spectroscopy (the study of light that has been
emitted from, reflected from, or shone through a gas, liquid, or
solid). But I don't know that the Raman effect had much...um...effect
on the rest of us. However, these days there are a lot of utilities
in many different fields. Here's a practical one: a Raman scanner is
a hand held device used to detect drugs, explosives, hazardous
chemicals, gases, and so forth. It is used by narcotics squads,
airport security, forensic detectives, and security experts.
For
more...
Check
out this article
on other Indian scientists.
Also
on this date:
Plan
ahead:
Check
out my Pinterest boards for:
And
here are my Pinterest boards for:
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