# Rayleigh Criterion or Resolving Power?

1. Feb 18, 2014

### Sastronaut

1. The problem statement, all variables and given/known data

I must compare the diffraction limit of the hubble telescope (2.4 meter) observing 500nm and a 100m telescope observing radiowaves with a wavelength of 21cm. I am asked to then explain why radio telescopes must be bigger!

2. Relevant equations

3. The attempt at a solution
I understand why it must be larger (The wavelength of radio light is much larger than optical (on the scales of meters as opposed to nm), so to be able to resolve objects with small angular sizes, you have to use a much larger telescope), but my question pertains to Rayleigh Criterion. My professor never taught us this. My question is Rayleigh Criterion the same as RP power. The equation given to use for resolving power is (2.5x10^5)(wavelength of light/diameter of telescope)

2. Feb 18, 2014

### Dick

Yes, the Rayleigh Criterion is the same as resolving power. Just compare (wavelength)/(diameter) in both of your cases.