What will happen if we try to reconstruct signal using phase only or magnitude only? I am studying Fourier Transform and it's inverse. We get phase and magnitude from Fourier transform and reconstruct it back from both together
My question is that 

  
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*What will happen if we try to  reconstruct given signal back using it's magnitude only with any random phase values?
  
*What will happen if we try to reconstruct given signal back using it's phase only with any random magnitude values?


Not in general. 
A set of conditions is given in this paper: 
Hayes, Monson H., Jae S. Lim, and Alan V. Oppenheim. "Signal reconstruction from phase or magnitude." Acoustics, Speech and Signal Processing, IEEE Transactions on 28.6 (1980): 672-680.
