1000 Solved Problems in Modern Physics

Chapter 2

Quantum Mechanics – I

2.1 Basic Concepts and Formulae

Wave number

ν ̃=

1

λ

(2.1)

1fm= 10 −^15 m; 1A ̊ = 10 −^10 m; 1 nm = 10 −^9 m; 1μm = 10 −^6 m;c =

197 .3Mev−fm

Photon energy

E=hv (2.2)

Photon momentum

p=hν/c

Photon energy−wavelength conversion

λ(nm)=

1241

E(eν)

(2.3)

de Broglie wavelength

λ=h/p (2.4)

λ(electron) :λ(A) ̊ =(150/V)^1 /^2 (2.5)

λ(neutron) :λ(A) ̊ = 0. 286 E−^1 /^2 (Ein ev) (2.6)

Atomic units
The Bohr radius^2 /mee^2 is frequently used as the unit of length in atomic physics.
In atomic units the energy is measured in multiples of the ionization energy of
hydrogen atom that ismee^4 /^2 ^2. In these units^2 =1,e^2 =2 andme=^12 in
all equations.

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