  We present estimates of the angular power spectra of the synchrotron
radiation intensity fluctuations at 6 and 20 cm for the shell type supernova
remnant Cas A and the filled-centre Crab supernova remnant. We find that the
intensity fluctuations of both sources have a power law power spectrum with
index -3.24 +/- 0.03. This power law power spectrum is consistent with the
magnetohydrodynamic turbulence in the synchrotron emitting plasma. For Cas A,
there is a break in the power spectrum and the power law index changes from
-3.2 to -2.2 at large angular scale. This transition occurs at an angular scale
that corresponds to the shell thickness of Cas A. We interpret this as a
transition from three dimensional turbulence to two dimensional turbulence on
scales that are respectively smaller and larger than the shell thickness.
