UGS 303 Lecture 24: The Global Diffusion of the Alphabet

Virtually every item sold in a store has a 12-digit UPC barcodewhich is scanned at the checkout counter. The first 11 digits of aUPC number d1d2d3 ? ? ? d11d12 identify the manufacturer andproduct. The last digit d12 is a check digit which is chosen sothat 3d1+d2+3d3+d4+3d5+d6+3d7+d8+3d9+d10+3d11+d12 =0 pmod10q.

If the congruence does not hold, an error has been made and theitem must be scanned again, or the UPC code entered by hand. Whichof the following UPC numbers were scanned incorrectly?

Consider the spectroscopic techniques (short answers please)

1) what kind of photons do NMR instruments detect?

2) what do these photons tell you about the molecule being scanned?

3) what kind of photons do IR spectrometers detect?

4) what do these photons tell you about the molecule being scanned?

5) what advantages and disadvantages do each technique have?

Are there any short or long term effects apparent in tissues ifa zone (or the whole) of human body is scanned with ultrasonicwaves often?