Attenuation cross section and molar attenuation coefficient are related by ε ε i = N A ln ⁡ ⁡ ( 10 ) σ σ i , and number density and amount concentration by τ τ = ℓ ℓ ∑ ∑ i = 1 N σ σ i n i , A = ℓ ℓ ∑ ∑ i = 1 N ε ε i c i . c i = n i N A , where N A is the Avogadro constant. In case of uniform attenuation, these relations become T = exp ⁡ ⁡ ( − − ℓ ℓ ∑ ∑ i = 1 N σ σ i n i ) = 10 ∧ ∧ ( − − ℓ ℓ ∑ ∑ i = 1 N ε ε i c i ) , or equivalently τ τ = ℓ ℓ ∑ ∑ i = 1 N σ σ i n i , A = ℓ ℓ ∑ ∑ i = 1 N ε ε i c i . τ τ = ℓ ℓ ∑ ∑ i = 1 N σ σ i n i , A = ℓ ℓ ∑ ∑ i = 1 N ε ε i c i . Cases of non-uniform attenuation occur in atmospheric science applications and radiation shielding theory for instance.