Max Frequency Homework: 9.0 ev Electron & 143 Neutrons, 92 Protons

[aurao2003]

Homework Statement

Hi
I am solving the june 2009 Physics 1 paper (Syllabus A). The mark scheme answer has got me slightly confused on 2 questions:

1. Calculate the maximum frequency of the photon emitted when the 9.0 ev
electron collides with an atom.

2.Calculate the specific charge of an isotope with 143 neutrons and 92 protons

Homework Equations

1) E= hf

2) Specific charge= charge/mass

The Attempt at a Solution

1)f= E/H
Therefore
f= 9 x 1.6x 10^-19/6.63 x 10^-34

But the schemes answer is very different to mine.

2)In the schemes answer, the mass was calculated as both 143 and 92. I presumed that the nucleon number constituted the mass, while the electrons (or number of protons) constituted the charge. (Multiplied by 92 in this case).

Anybody? Thanks.

 

[Delphi51]

Your #1 calc looks good to me. Could it be some silly error in calculating? I got 2.17 x 10^15 Hz. What is the specified answer?

For #2, the mass is 143+92 (protons and neutrons have practically the same mass), so it is 92/(143+92) in electron charges per nucleon mass. Conversion of units may well be necessary.

 

[aurao2003]

Thanks. I am fine now.