An electron in a one-dimensional region of length L is described by the wavefunction ψn(x) = sin(nπx/L), where n = 1, 2, …, in the range x = 0 to x = L; outside this range the wavefunction is zero. The orthogonality of these wavefunctions is confirmed by considering the integralI= ∫0L sin(nπx/L)sin(mπx/L)dx(a) Use the identity sinAsinB = 1/2{cos(A-B)-cos(A+B)} to rewrite the integrand as a sum of two terms. (b) Consider the case n = 2, m = 1, and make separate sketch graphs of the two terms identified in (a) in the range x = 0 to x = L. (c) Make use of the properties of the cosine function to argue that the area enclosed between the curves and the x axis is zero in both cases, and hence that the integral is zero. (d) Generalize the argument for the case of arbitrary n and m (n ≠ m).
An electron in a one-dimensional region of length L is described by the wavefunction ψn(x) = sin(nπx/L), where n = 1, 2, …, in the range x = 0 to x = L; outside this range the wavefunction is zero. The orthogonality of these wavefunctions is confirmed by considering the integral
I= ∫0L sin(nπx/L)sin(mπx/L)dx
(a) Use the identity sinAsinB = 1/2{cos(A-B)-cos(A+B)} to rewrite the integrand as a sum of two terms. (b) Consider the case n = 2, m = 1, and make separate sketch graphs of the two terms identified in (a) in the range x = 0 to x = L. (c) Make use of the properties of the cosine function to argue that the area enclosed between the curves and the x axis is zero in both cases, and hence that the integral is zero. (d) Generalize the argument for the case of arbitrary n and m (n ≠ m).
Trending now
This is a popular solution!
Step by step
Solved in 4 steps with 6 images
