Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Topic started by: rleung on November 19, 2005, 05:24:45 PM
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Hi,
Ok, I am either going crazy or the book is messed up. I am using Bruice's textbook (4th edition), and on pg. 326, it says that a red shift is a shift to a longer wavelength, while a blue shift is a shift to a shorter wavelength. However, in the chart found further below on the same page (chart of the dependence of the color observed on the wavelengh of light absorbed), it lists red light as having a wavelength absorbance of 440-560 nm, while blue light has a wavelength absorbance of 540-650 nm, which is OPPOSITE of what it said earlier that red light having a longer wavelength.
I am very confused. Is there anyone that could help? I would much appreciate it. Thanks so much.
Ryan
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Red is definitely at longer wavelength end. Check out http://en.wikipedia.org/wiki/Electromagnetic_spectrum (http://en.wikipedia.org/wiki/Electromagnetic_spectrum) (scroll down to visible radiation).
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Hi,
Ok, I am either going crazy or the book is messed up. I am using Bruice's textbook (4th edition), and on pg. 326, it says that a red shift is a shift to a longer wavelength, while a blue shift is a shift to a shorter wavelength. However, in the chart found further below on the same page (chart of the dependence of the color observed on the wavelengh of light absorbed), it lists red light as having a wavelength absorbance of 440-560 nm, while blue light has a wavelength absorbance of 540-650 nm, which is OPPOSITE of what it said earlier that red light having a longer wavelength.
I am very confused. Is there anyone that could help? I would much appreciate it. Thanks so much.
Ryan
read up on hypsochromic and bathochromic shifts, don't take "red" and "blue" literally.
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Read up on absorbing of light. The chart you were looking at was about the dependence of the color observed on the wavelength of light absorbed. It is not saying that red light is at a wavelength of 440-560 nm.
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Hmm, I understand now that the chart was not referring to the wavelength of red light, but I am not sure what the chart title means. Does it mean that the wavelength indicated is the wavelength of light that is ABSORBED in order to REFLECT back that certain color (in this case, red)?
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blue light is of course of a shorter wavelength than the red one
but the complementry colour of the blue light would be at a longer wavelength than that of red
if u want to know further see an analytical chemistry textbook talking about spectrophotometry
key phrase:for a substance to appear blue it must absorb all wavelengthes except the blue one
and one of the absobed wavelengthes is absorbed maximum