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Crap! / Re: post music that kwiftee likes
« on: April 22, 2012, 05:42:33 pm »
i am mildly perplexed by this thread
but you guys seem to be doing alright so far.
but you guys seem to be doing alright so far.
Chat button has been eaten. Click here to join in the idling fun!
By the way, I've been stuck on this physics question for a while now.
When light of wavelength 2.08 * 10^-7 m falls on a photosurface, a voltage of 1.40 V is required to stop the emitted electrons from reaching the anode. What is the largest wavelength of light that will result in the emission of electrons from this photosurface?
I was thinking since V = E/Q then E = 1.40 * 1.6 * 10-19 which gives E = 2.24 * 10^-19 J, then sub in this value for E = hfc and since h is just planck's constant then you just solve for the critical frequency. Then you use λ = c / f where 'c' is the speed of light and 'f' is the critical frequency, resulting in a wavelength of 8.9 * 10^-7 m, but the answer in my textbook says it's 2.7 * 10^-7 m
halp