L04_LightParticlesPhotonsNOTES

L04_LightParticlesPhotonsNOTES - Slide 3 © 2006 M.Kubinec...

Info iconThis preview shows pages 1–4. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Slide 3 © 2006 M.Kubinec, A. Pines L4-3 x-rays rays Electromagnetic Spectrum Electromagnetic Spectrum 400 400 600 600 500 500 700 700 nm nm Visible Visible γ-rays rays IR IR Radio, NMR, MRI Radio, NMR, MRI MW MW ν λ 10 10 10 10-4 10 10 8 10 10 4 10 10-8 10 10-12 12 10 10-16 16 UV UV m The electromagnetic spectrum is composed of various named bands of radiation from the very short wavelength, high frequency gamma rays to long wavelength, lower frequency radiowaves. All the flavors of electromagnetic radiation (EMR) in the spectrum can be described as wave phenomena with a wavelength, frequency and speed relationship lamda( λ ) x nu( ν ) = c. So far we have not discussed the how the intensity or the energy (two very different things) of the radiation is related to the wave nature of the light. Slide 4 © 2006 M.Kubinec, A. Pines L4-4 Chem Quiz 4.1 Chem Quiz 4.1 I o 1) 1) I 3) 3) 2) 2) I 8 4 What is the What is the intensity intensity of of light light emerging from emerging from two two columns columns ? I o 2 I o ? Let’s consider the intensity issue in the form of a chemquiz. We have seen we can place filters in the path of a beam of light and completely remove (absorb) certain wavelengths. We can also partially absorb, or simply attenuate (reduce) the light that is transmitted. You will see in lab that the amount of attenuation depends on the properties of the filter (its concentration, if it is a dissolved chemical as we used previously) and the path length the light passes through. If a filter is used that reduces the intensity Io of a light beam by ½, what intensity would be transmitted from two consecutive filters? [question]: What is the intensity of light emerging from two columns? [choices]: I /4, I /8, 0 Slide 5 © 2006 M.Kubinec, A. Pines L4-5 Chem Quiz 4.1 Solution Chem Quiz 4.1 Solution I o 1) 1) I 3) 3) 2) 2) I 8 4 I o 2 I o I 4 If a single filter reduces the intensity by ½, then this will continue to be the case, and the intensity will be reduced by ½ again as it passes through the second filter. The total reduction in intensity will be ¼. [solution]:1, I o /4 Slide 6 © 2006 M.Kubinec, A. Pines L4-6 Light Intensity Light Intensity E photon photon = h ν The Particle Nature of Light The Particle Nature of Light An interesting question is: how many times can we repeat the reduction in intensity by ½? We could perform this ‘thought experiment’ with matter. Keep dividing a piece of a pure element by half. Eventually we would reach the individual atoms and any further division would change the fundamental properties (i.e. it wouldn’t be the same element). This is a thought experiment proposed by Democretus, who proposed the existence of atoms (‘not divisible’) parts of matter. If we perform the same experiment with light, we understand that the light would get dimmer and dimmer. Imagine doing this with visible light in a perfectly dark room (no other light whatsoever). What would you see after the light dimmed to apparently zero? light dimmed to apparently zero?...
View Full Document

This note was uploaded on 08/12/2008 for the course CHEM 1A taught by Professor Nitsche during the Fall '08 term at Berkeley.

Page1 / 8

L04_LightParticlesPhotonsNOTES - Slide 3 © 2006 M.Kubinec...

This preview shows document pages 1 - 4. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online