## Homework Problem 1b.15

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

Emma Randolph 1J
Posts: 65
Joined: Fri Sep 28, 2018 12:29 am

### Homework Problem 1b.15

For homework problem 1B.15, they ask: The velocity of an electron that is emitted from a metallic surface by a photon is 3.6 3 103 km?s 21. (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?

In order to find the wavelength for part a, would I plug it in to DenBroglie's wave equation? If I do, how do I determine what the momentum is? Is the mass of photons the same for every atom? I'm confused.

Thanks!

ChathuriGunasekera1D
Posts: 78
Joined: Fri Sep 28, 2018 12:17 am

### Re: Homework Problem 1b.15

Hi! I think you mean mass of electron. Photons have no mass, so because this question asks "what is the wavelength of the ejected electron" you use De Broglie's equation. The mass of an electron is always the same, regardless of the element. I think it's 9.11 x 10^-31 kg and you have to leave it in kg.

gillianozawa4I
Posts: 31
Joined: Fri Sep 28, 2018 12:27 am

### Re: Homework Problem 1b.15

Yes, you would plug it into de Broglie's equation. Momentum is found by multiplying mass of the electron by the velocity, and mass of the electron is given on the formula sheet. The equation gives the velocity, so you would just have to multiply these two values to get momentum. Hope this helps!