what is the frequency of this photon?

Question

can someon please help me with this question:

a photon, 12.1 eV is emitted, and it says find the:
a) frequency
b)wavelength

Answer 1

Whenever you are given something in eV, try converting it to the unit of energy joules.

eV means electron volts



1eV is the kinetic energy gained by an electron when it is accelerated in a pd of 1 V.



1eV= 1.6*10^-19 J



Hence 12.1 eV= 12.1*1.6*10^-19 J=1.936E-18 J ( E means 10^)



a) To calculate the photon frequency use E=hf

h=6.63×10−34 Js

f=1.936E-18 / 6.63×10−34 = 2.92*10^15 Hz



b) v=f λ

λ=v/f = 3E8/ 2.92E15 = 1.02*10^-7 m

Answer 2

E = h*f



where h is Planck's constant. Using the form of Planck's constant with the right units...

4.136*10^(-36) eV*s



12.1 eV / 4.136*10^(-36) eV*s = f

2.9255*10^36 (1/s) = 2.9255*10^36 Hz = f



It's nifty to look at the units of speed and distance... m/s and m where 1/s is Hz

so if you divide speed by distance you get units of Hz

It so happens this is the case as you can see with the equations on the wikipedia page attached.

(Note that they use v the greek letter nu as frequency and c for the speed of light)



f = c/lambda

Answer 3

E=hv



where

E = energy

h = Planck constant (4.136 x 10^-15eV/s)

v = frequency (v= c/lambda)

c= speed of light (3x10^8m/s)