Question

The number of particles is given by n = -D [2−1/ 2−1] are crossing a unit area perpendicular to x-axis in unit time. n1 and n2 are the number of particles per unit volume for the value of x meant to be x1 and x2. What is the dimensional formula of diffusion constant D?

Answer 1

N= no. of particle per unit area per unit time

n1 & n2 = no. of particle per unit volume

x1 & x2 are distance from some reference point.

Dimension of ′N′=[L−2T−1]

Dimensional formula of n1 & n2 =[L−3]

Dimensional formula of x1 & x2 = [L]

N=−Dx2−x1n2−n1

D=−N[n2−n1x2−x1]

=[L−3][L−2T−1][L]

D=[