## Problem B.15

kevinchang_4I
Posts: 55
Joined: Tue Nov 13, 2018 12:17 am

### Problem B.15

This problem gives the velocity of an emitted electron and asks for its wavelength. How do I solve this without a given work function? Thank you for the help

Benjamin Feng 1B
Posts: 102
Joined: Sat Sep 07, 2019 12:19 am

### Re: Problem B.15

You can use the deBroglie relation lambda = h/p. To find the wavelength, you know h the constant, and can find momentum p by multiplying mass times velocity of the electron.

Posts: 87
Joined: Sat Aug 24, 2019 12:15 am

### Re: Problem B.15

a)
ƛ = h/p ƛ = h/mv

3.6 X 10^3 km x 1000m/1km = 3.6 X 10^3 m

(6.62 X 10^/34 J/s)/ (9.2109x10^-31 kg) (3.6 x 10^6 m/s)
=
2.0 X 10^-10 m
ƛ = 2.0 X 10^-10 m
b)
E=hv Hz = 1/s
E = (6.6 x 10^-34 J/s) (25 X 10^6 Hz)
E = 1.66 X 10^-17 J

c)
E = 1/2 m v^2
E = 1/2 (9.10938 X 10^-31 kg) (3.6 x 10^6 m/s)^2
E = 2.25 X 10^-17 J

E = 5.9 X 10^-18J + 1.66 X 10^-17J
E = 2.25 X 10^-17 J

ƛ = (6.6 X 10^-34 J/s) (2.99 X 10^8m/s)/ (2.25 X 10^-17 J) =
8.8 X 10^-9 m
8.8 nm

d) this is the y-ray radiation.