Google Answers Logo
View Question
Q: Does a prism refract all electromagnetic waves? ( Answered 5 out of 5 stars,   4 Comments )
Subject: Does a prism refract all electromagnetic waves?
Category: Science > Physics
Asked by: rambler-ga
List Price: $10.00
Posted: 12 Mar 2005 10:53 PST
Expires: 11 Apr 2005 11:53 PDT
Question ID: 493299
Does a prism refract ALL electromagnetic waves (including x-rays and
gamma rays, etc), or just visible light?
Subject: Re: Does a prism refract all electromagnetic waves?
Answered By: siliconsamurai-ga on 12 Mar 2005 14:12 PST
Rated:5 out of 5 stars
Hi, thank you for submitting your question to Google Answers, I hope I
can provide the information you are seeking.

The short answer is no, a glass prism is essentially transparent to
most forms of electro-magnetic radiation.

The visible light spectrum is a very narrow band out of a very large spectrum.

Visible light ranges from about 700 nanometers (.00000007) meters to 400 nm.

At the two extreme ends of the spectrum lie radio waves (you know they
pass right through glass) and, at the other end, gamma radiation
(which passes through almost anything for some distance but, along
with ultraviolet is absorbed by ozone, luckily for us).

or for a more advanced look

Refraction and even reflection take place according to the exact
frequency of the radiation which explains why a prism can spread light
into the spectrum.

I?m not certain how much detail you want so for a very detailed explanation, see

For historical interest, this was all discovered and explained by (who
else?) Issac Newton in his book Opticks (not a misspelling). I know a
reproduction used to be available from Dover Publications.

It may still be available on CD from

Here?s an interesting tutorial on the whole spectrum

Although other wavelengths can?t be refracted or reflected by a glass
prism, they can be by other things such as a strong magnetic field.

They can also be diffracted, which is similar, by reflecting them from
a glass-like sodium chloride (table salt) crystal.

This and other substances which can reflect X-rays do so from the
surface and depend on the spacing of atoms in the crystal matrix.

You can learn more about how X-rays react at

and calculate the index of refraction at

I did find a specific report on your precise question taken from Dr.
W. C. Roentgen who discovered X-rays.

It says in part, Dec. 1895,
?After I had recognized the transparency of various substances of
relatively considerable thickness, I hastened to see how the X-rays
behaved on passing through a prism and to find whether they were
thereby deviated or not.
Experiments with water and with carbon disulphide enclosed in mica
prisms of about 30 degrees refracting angle showed no deviation,
either with the fluorescent screen or on the photographic plate. For
purposes of comparison the deviation of rays of ordinary light under
the same conditions was observed; and it was noted that in this case
the deviated images fell on the plate about 10 or 20 mm distant from
the direct image. By means of prisms made of hard rubbers and of
aluminum, also of about 30 degree refracting angle, I have obtained
images on the photographic plate in which some deviation may perhaps
be recognized. However, the fact is quite uncertain; the deviation, if
it does exist, being so small that in any case the refractive index of
X-rays in the substances named cannot be more than 1.05 at the most.
With a fluorescent screen I was unable to observe any deviation.?

Thank you again for turning to Google Answers for your research needs.
rambler-ga rated this answer:5 out of 5 stars and gave an additional tip of: $2.00
Thanks for the quick answer, and for providing all the links.

Subject: Re: Does a prism refract all electromagnetic waves?
From: puffin88-ga on 12 Mar 2005 12:49 PST
The first thing I'll say is that since glass doesn't conduct
electricity (and since they use glass windows on microwave ovens) I'm
inclined to guess that there are some frequencies of electromagnetic
waves that not only don't get refracted, they don't even get into the
glass at all.  The glass reflects them, just like a brick wall
reflects the beam from a flashlight.

But anyway, it might be worth remembering two things:
1) The refraction happens because the speed of light in glass is
different than the speed of light in air.
2) The prism's refraction creates a rainbow because the change of the
light's speed in the glass depends on the light's wavelength.  That
means that the blue in the light refracts differently than the red
does, which has the effect of separating the colors from each other.

(I have the feeling that you are asking about that rainbow effect,
instead of just the refraction phenomenon.  That's because you asked
about a prism instead of, say, a fishtank, which also refracts
light...but isn't shaped right to give a dramatic separation of

So, keeping those two things in mind, we can now see that your
question can be restated as:
"Give the formula for the speed of light in glass as a function of
wavelength.  Does it give different speeds no matter what wavelength
you put in?"

If the speed continues to change for values of the wavelength that
very very large or very very small, that would predict that the prism
does continue to act "prisimatically", over that very large range of
electromagnetic waves.  However, if the speed stops changing much when
the wave lengths get very long or very short, then that would mean
that the degree of refraction gets to be about constant and the prism
acts more and more like a fishtank -- bending the light, but not
separating out its frequencies.

(caveat: now that I have written this, it occurs to me that I don't
*really* know if it's right.  I think it's right, but I'd be happy to
have someone correct it.)
Subject: Re: Does a prism refract all electromagnetic waves?
From: xarqi-ga on 12 Mar 2005 15:05 PST
Just some comments on some comments.

Microwaves do not escape from a microwave oven because glass is opaque
to them, it is the presence of the wire mesh in or on the glass that
forms part of a Faraday cage that is responsible.

From memory, electromagnetic radiation is not bent in an magnetic
field.  This applies to electrically charged particles only (Correct
me please if I am wrong, but a cursory web search didn't produce
anything to refute my memory).
Subject: Re: Does a prism refract all electromagnetic waves?
From: guzzi-ga on 12 Mar 2005 19:43 PST
Yea you?re right xarqi. Well, there is actually certain interaction
between magnetic fields and electromagnetic waves but not relevant to
the question. And though puffin88 you were not completely correct, it
was with such grace :-)

Regarding the question though, prisms do affect other wavelengths --
if the material is appropriate. Transparency of a material above a
certain frequency is determined by a quantum definition, ?the plasma
frequency?. There are other factors which prevent transparency at
various frequencies but it?s quite a big subject.

Germanium, a black opaque element, is used for infra red lenses. In
theory it could be used as a prism but the chromatic dispersion is low
so it?s not very good. Certain plastics are used for microwave lenses,
often in the form of fresnel (aka incorrectly frenel) and look like
miniature lighthouse lenses. There are better ways to split microwave
frequencies though.

Subject: Re: Does a prism refract all electromagnetic waves?
From: siliconsamurai-ga on 12 Mar 2005 22:25 PST
Thank you for the nice rating and the tip.

Important Disclaimer: Answers and comments provided on Google Answers are general information, and are not intended to substitute for informed professional medical, psychiatric, psychological, tax, legal, investment, accounting, or other professional advice. Google does not endorse, and expressly disclaims liability for any product, manufacturer, distributor, service or service provider mentioned or any opinion expressed in answers or comments. Please read carefully the Google Answers Terms of Service.

If you feel that you have found inappropriate content, please let us know by emailing us at with the question ID listed above. Thank you.
Search Google Answers for
Google Answers  

Google Home - Answers FAQ - Terms of Service - Privacy Policy