Electron Volt (eV)
By DarthVader
Date: 2022-06-11
Topic: 123 see comments
Post views: 1047
Electron Volt (eV)
1 eV is equal to 1 electron with charge ‘e' (e = 1.6 x 10-19 C) moving through a potential difference of 1 volt.
1 eV = 1.6 × 10-19 C × 1 V = 1.6 × 10-19 J
Energy Of A Photon
The energy of a photon E is given by:
E = ( 1.24 / λ ) eV
Where λ has units of μm and is the wavelength associated with the photon.
Energy Of The Sun Hitting The Earth
The energy of photons of sunlight reaching the surface of the earth falls within the range 12.4 eV (UV) to 1.24 eV (IR).
UV light at shorter wavelengths (less than 100 nm) is not included in this range; such light is absorbed before it reaches the Earth's surface.
eV
The measurement of the eV is derived from 2 equations from the property of waves:
E = hf
and:
c = fλ
Combining these 2 equations by substituting the value of f from the second equation into the first gives a relationship between the energy of a photon and the wavelength of light, λ:
E = hc / λ
Substituting the values of the 2 constants gives:
E = ((6.626 × 10-34 J s) × (2.998 × 108 m s-1)) / (λ)
Which equals:
E = (1.99 × 10-25) / (λ) J
To arrive at the eV, this value of energy is divided by the charge of an electron (1.6 × 10-19 coulombs, C):
E = ((1.99 × 10-25) / (λ)) J × ((1) / (1.6 × 10-19 C)) × 1 × 106
And this creates the equation for calculating the energy of a photon:
E = (1.24) / (λ) eV
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