In which Lindsay attempts to teach herself Physics…

10 03 2008

Am I wrong, or do photons with wavelengths in the visible light spectrum interact with matter far more frequently than photons of different wavelengths? For example, visible light is reflected/absorbed by matter – thus allowing us to see things. Ultra Violent photons (I believe) have such a high frequency, that they penetrate matter that visible light does not, and yet, Radio Waves, which have a lower frequency than visible light, also pass through things that visible light does not. (You can listen to a radio in a windowless room, but you can’t see the sunlight through the walls.)  So why is it that visible light seems to be the most “blockable” wavelength of light?

I could be missing some very important and relative information. Please enlighten me if you can!

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4 responses

11 03 2008
Bobbie!!

Hi Lindsay :)
If you had a thin enough wall – say in a paper house – the sun would surely shine through. Though you seem to understand what frequency is – it’s the wavelength part maybe you struggle with. If the light was brighter than sunlight it would in fact shine into a windowless room (hey maybe one day! – the sun is growing, right?)
The wavelength (not frequency) of radio waves are verrry large and think nothing of a wall. Try to listen to the radio in a tunnel though, and you will find it impossible.

Hope any of this helps.
<3Bobs the x-physicist

11 03 2008
gowithgravity

A couple thoughts:
Ultraviolet light is pretty readily scattered/absorbed by most stuff. Higher frequency light, like X-rays and higher, can more efficiently penetrate matter.

You’re at least partially on to something. Light that’s fairly close in wavelength to visible light is in the part of the spectrum that interacts efficiently with the electronic structure of atoms, making scattering/absorption much more likely.

Wavelength and frequency are inversely proportional, and have nothing to do with brightness/intensity.

At the risk of being too pedantic, check out http://en.wikipedia.org/wiki/Electromagnetic_spectrum – including the atmospheric opacity image on the right.

12 03 2008
Bobbie (again)

One more thing,
It’s no coincidence that we evolved to see “visible light.”

13 03 2008
Lindsay

Thanks to both of you for your responses! I also went over the issue with one of my professors, and I think I’m beginning to have a little bit of a better grasp on light. (It’s so interesting to think I could go for 20 years without fully grasping the concept!) Light is quite fascinating, add magnetism and it becomes even more exciting to try to puzzle out.

And Bobbie – I believe I understand how we evolved to see visible light. Our sun radiates mostly in the visible light, thus it is no coincidence that we see “visible light”. Perhaps if we were orbiting a star which radiated more Ultra Violet light, we would “see” in Ultra Violet. (In which case the sun would also be hotter and more massive…)

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