Rayleigh Criterion or Resolving Power?

In summary, when comparing the diffraction limit of the Hubble telescope observing 500nm and a 100m telescope observing radiowaves with a wavelength of 21cm, it is clear that the radio telescope must be much larger due to the larger wavelength of radio light. This allows for better resolution of objects with small angular sizes, and is represented by the Rayleigh Criterion or resolving power equation.
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Sastronaut
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Homework Statement



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!

Homework Equations





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)
 
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  • #2
Sastronaut said:

Homework Statement



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!

Homework Equations





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)

Yes, the Rayleigh Criterion is the same as resolving power. Just compare (wavelength)/(diameter) in both of your cases.
 
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1. What is Rayleigh Criterion or Resolving Power?

The Rayleigh Criterion or Resolving Power is a measure of the ability of an optical instrument, such as a telescope or microscope, to distinguish between two closely spaced objects. It determines the smallest angular separation at which two objects can be resolved and seen as two separate entities. It is named after the British physicist Lord Rayleigh who first proposed it in the 19th century.

2. How is the Rayleigh Criterion calculated?

The Rayleigh Criterion is calculated by dividing the wavelength of the light being used by the diameter of the objective lens or mirror. This gives the smallest angular separation between two objects that can be resolved by the instrument, also known as the angular resolution. The larger the diameter of the objective, the smaller the angular resolution, and the better the resolving power of the instrument.

3. What is the relationship between Rayleigh Criterion and the size of the aperture?

The Rayleigh Criterion is directly proportional to the size of the aperture, or the diameter of the objective lens or mirror. This means that as the aperture size increases, the resolving power of the instrument also increases. This is because a larger aperture allows more light to enter the instrument, resulting in a higher spatial resolution and better ability to distinguish between closely spaced objects.

4. Can the Rayleigh Criterion be used for all types of optical instruments?

Yes, the Rayleigh Criterion can be used for all types of optical instruments as long as they use light as the source of imaging. This includes telescopes, microscopes, cameras, and even the human eye. However, it is important to note that other factors such as atmospheric conditions, lens quality, and magnification also affect the resolving power of these instruments.

5. How is the Rayleigh Criterion used in astronomy?

In astronomy, the Rayleigh Criterion is used to determine the smallest angular separation at which two celestial objects, such as stars, can be resolved by a telescope. This is important in studying binary star systems and other celestial objects that are closely spaced. It also helps astronomers in determining the quality and resolving power of different telescopes and their ability to capture high-resolution images of distant objects in space.

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