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Wavelength Calculation

Posted: Tue Oct 23, 2018 7:00 pm
by Lily Benitez 2G
The velocity of an electron that is emitted from a metallic surface by a photon is 3.6 x 10^3 km/s . (a) What is the wavelength of the ejected electron? (b) No electrons are emitted from the surface of the metal until the frequency of the radiation reaches 2.50 x 10^16 Hz. How much energy is required to remove the electron from the metal surface? (c) What is the wavelength of the radiation that caused photoejection of the electron? (d) What kind of electromagnetic radiation was used?

I understand how to do parts a and b, but I am confused on part c. I used the frequency given to us and substituted it into the equation c= (frequency x wavelength). The correct answer should be 8.8 nm but I got 12 nm. Am I supposed to use a different equation to calculate the wavelength?

Re: Wavelength Calculation

Posted: Tue Oct 23, 2018 8:24 pm
by Francis_Nguyen3D
Use the equation Energy= hc/(wavelength).
Then use the energy of the photon you got from part b, which should be 2.25 x 10^-17J.
Rearrange the equation so that you are solving for wavelength so it would be: wavelength= hc/energy
Then plug in 6.626 x 10^-34 for h and 3.0 x 10^8 for c and divide by 2.25 x 10^-17 and you should get around 9nm.
The book gets 8.8nm from using the unrounded numbers for Planck's constant and the speed of light.

Re: Wavelength Calculation

Posted: Tue Oct 23, 2018 10:05 pm
by Lily Benitez 2G
Thank you