Page 1 of 1

hw 1B.15 part c

Posted: Sat Oct 19, 2019 2:43 pm
by Joanna Mendoza 3J
Problem: The velocity of an electron that is emitted from a metallic surface by a photon is 3.6 x 10^3 km.s^-1. (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 3 1016 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 was able to solve parts a and b but what equation would I use to be able to solve c? Can somebody show me the steps and explain to me why they are done?

Re: hw 1B.15 part c

Posted: Sat Oct 19, 2019 3:06 pm
by Andrew Jang 4D
You should find the energy of the photon that caused the electron to eject as well as move at 3.6*10^3 km/s. You already found the energy required to eject the electron from the metal surface in part B, so all you need now is the kinetic energy of the electron that makes it move at its speed. You can use (1/2)mv^2 to find it. Once you add that to your answer from part B, you get the total energy of the photon. From there, you can use E=hv and c=λv to find the wavelength λ.

Re: hw 1B.15 part c

Posted: Sun Oct 20, 2019 4:03 pm
by Joanna Mendoza 3J
Thank you for explaining that clearly!
For part d, how would I determine the kind of electromagnetic radiation that was used?

Re: hw 1B.15 part c

Posted: Sun Oct 20, 2019 9:35 pm
by Jesalynne 2F
I think you would use the wavelength you got from part c and find where it is on the electromagnetic spectrum. There is a figure and table in 1A.2 Electromagnetic Radiation that you can refer to.