MATLAB Rayleigh fading and white gaussian noise

From the MATLAB code below where do these theoretical equations for Rayleigh fading and white Gaussian noise come from? Or how are they derived?

h = 1/sqrt(2)*[randn(nrx,ntx,N/ntx) + 1i*randn(nrx,ntx,N/ntx)]; % Rayleigh channel
n = 1/sqrt(2)*[randn(nrx,N/ntx) + 1i*randn(nrx,N/ntx)]; % white gaussian noise, 0dB variance