### 1.33 Part A

Posted:

**Mon Oct 16, 2017 10:42 pm**Here's the question:

The velocity of an electron that is emitted from a metallic surface by a photon is 3.6 * 10^3 km/s. (a) What is the wavelength of the ejected electron?

I tried doing this question two ways: once using the de Broglie equation, which gave me the right answer (2.0*10^-10m), and once using Ek = 1/2mv^2, which gave me the wrong answer (3.366*10^-8m).

I thought both of these methods would theoretically give me the same answer.

Is there a way to tell which equation is the right one to use?

The velocity of an electron that is emitted from a metallic surface by a photon is 3.6 * 10^3 km/s. (a) What is the wavelength of the ejected electron?

I tried doing this question two ways: once using the de Broglie equation, which gave me the right answer (2.0*10^-10m), and once using Ek = 1/2mv^2, which gave me the wrong answer (3.366*10^-8m).

I thought both of these methods would theoretically give me the same answer.

Is there a way to tell which equation is the right one to use?