•Real life example:
Ultra-Violet light hitting your skin (important in Laramie!)
–Threshold for chemical damage
set by energy (wavelength) of photons
•Below threshold (long
wavelengths) energy too weak to cause chemical changes
•Above threshold (short
wavelength) energy photons
can break apart DNA molecules
–Number of molecules damaged =
number of photons above threshold
–Very unlikely two photons can
hit exactly together to cause damage