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Thursday, April 30, 2015

Exploring Quantum Physics - Week 5 Problem 1

Question:

What value does Einstein quote for Lenard’s measurement of the “largest effective wavelength for air”? Express your answer as an integer in units of nanometers.

Solution:

Reading Einstein's original paper at wikisource, I found a line:

"According to Lenard's measurements for air the largest wavelength that has an effect is about 1.9·10-5 cm, so"

So the answer is $ 1.9 \times 10^{-5} \times 10^{-2} = 1.9 \times 10^{-7} = 190 \times 10^{-9} $ meters, or in other words, 190 nanometers.

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