Problem with units when using E=hv

  • Thread starter Thread starter Aspchizo
  • Start date Start date
  • Tags Tags
    Units
Aspchizo
Messages
26
Reaction score
0
In case I'm wrong, the formula for energy of a photon is E=hf.
Or E=hc/λ, because f=c/λ.

Basically the second formula is just in case you don't know frequency so it crams the equation for that into the equation for energy.

When I use E=hc/λ the units I get are...

kg*m2/s3

What I did was... A photon of red light, has a wavelength of like 700nM, so...

(6.626×10-34kg*m2/s2) (3x108m/s) / 7×107m

= 2.84×1019kg*m2/s3

I thought the answer would be in Joules, which is kg*m2/s2, so I must be missing something... Why the extra unit of time.
 
Physics news on Phys.org
Wow stupid, Planck's constant is J×s which is kg*m2/s

Well, everything else looks okay?
 
Check the signs of your exponents. Everything else looks right, if you fix your units.
 
Ah right, ^-19

Thanks
 

Thread 'Toponium Discovered'

Toponium is a hadron which is the bound state of a valance top quark and a valance antitop quark. Oversimplified presentations often state that top quarks don't form hadrons, because they decay to bottom quarks extremely rapidly after they are created, leaving no time to form a hadron. And, the vast majority of the time, this is true. But, the lifetime of a top quark is only an average lifetime. Sometimes it decays faster and sometimes it decays slower. In the highly improbable case that...
View full post »

Thread 'Dirac-Delta from Normalization of Continuous Eigenfunctions'

I'm following this paper by Kitaev on SL(2,R) representations and I'm having a problem in the normalization of the continuous eigenfunctions (eqs. (67)-(70)), which satisfy \langle f_s | f_{s'} \rangle = \int_{0}^{1} \frac{2}{(1-u)^2} f_s(u)^* f_{s'}(u) \, du. \tag{67} The singular contribution of the integral arises at the endpoint u=1 of the integral, and in the limit u \to 1, the function f_s(u) takes on the form f_s(u) \approx a_s (1-u)^{1/2 + i s} + a_s^* (1-u)^{1/2 - i s}. \tag{70}...
View full post »

Similar threads

Calculating the Planck Length
Replies
3
Views
207
Kinetic energy and velocity of electron after compton scatte
Replies
1
Views
4K
A CGS units confusions in plasma physics journal papers
Replies
22
Views
13K
Momentum of a Photon: E/c=p Explained
Replies
2
Views
2K
How do you derive the units for momentum for photons
Replies
4
Views
1K
Understanding cut off wavelength at edge of Bremsstrahlung region
Replies
1
Views
14K
Calculate the wavelength when electron transits.
Replies
2
Views
1K
Finding the momentum of a photon
Replies
11
Views
3K
Minimum wavelength of electrons ejected from metal
Replies
1
Views
2K
Peak wavelength and Spectral Bandwidth
Replies
4
Views
2K

Hot Threads

Recent Insights

Back
Top