According to quantum theory, the energy associated with a photon is given by
E = hf …(i)
Where
According to the mass-energy equivalence principle, the energy of a photon is
E = mc2 …(ii)
Where
From equation (i) and (ii), we have
hf = mc2
But frequency, f = c/λ
Where λ is wavelength
⇒ hc/λ = mc2
⇒ λ = h/mc
Instead of photon, we have material particle of mass m moving with velocity v, then
λ = h/mv
Where mv = p, momentum of the particle. Therefore
λ = h/p
Above expression is known as the expression for a de-Broglie wavelength that shows the wavelength associated with a particle of mass m moving with velocity v.
List I (Spectral Lines of Hydrogen for transitions from) | List II (Wavelength (nm)) | ||
A. | n2 = 3 to n1 = 2 | I. | 410.2 |
B. | n2 = 4 to n1 = 2 | II. | 434.1 |
C. | n2 = 5 to n1 = 2 | III. | 656.3 |
D. | n2 = 6 to n1 = 2 | IV. | 486.1 |