## 1B.15

$\lambda=\frac{h}{p}$

Ricky Ma DIS 4E
Posts: 72
Joined: Fri Sep 28, 2018 12:27 am

### 1B.15

The velocity of an electron that is emitted from a metallic surface by a photon is 3.6 x10^3km/s
(a) What is the wavelength of the ejected electron?

I understand now that you use the Debroglie equation. My problem is that I tried using the Ek=0.5mv^2 first then using lambda=hc/E to find the wavelength but I couldn't get the right answer. Is there a reason that that method does not work? I first turned the 3.6 x10^3km/s into meters then just plugged that into the "v" of Ek=0.5mv^2 but ended up with the wrong answer.

Thanks!

Michael Torres 4I
Posts: 92
Joined: Thu May 10, 2018 3:00 am
Been upvoted: 1 time

### Re: 1B.15

The problem with using (lambda) = hc/E in this case is that it can only be applied to light or something without rest mass. Because the electron has rest mass, DeBroglie's equation must be used.

(lambda) = hc/E can be used to find the wavelengths of electromagnetic radiation, whereas DeBroglie's equation can be applied to objects with rest mass.