Resolution power of telescope lab (rayleigh criterion)

[jmher0403]

I have done a lab on resolution power of a telescope.
a wire gauze was placed infront of sodium lamp and i used a telescope with adjustable vertical slit to look at it.

i was bit confused with the theory ..

1) I was told to record the slit width when the vertical wires just cease to be seen.
Do I take the record when it starts to disappear or when it fully disappears? It was really hard to tell the point where the dissapearance started. Any suggestions as to get more accurate data?

2) why would the vertical wires of the gauze disappear? I know the central maximum coinciding with first minimum but what's it got to do with the wires?? Is it because the light sources between the gauze wires coming together (max + min) canceled out so that the vertical wires are hidden?

3) I measured the distance between wires (x)
distance between gauze and the telescope (D)
width of slit (a)

and have equation

angular separation α = λ/ahow would I get the wavelength from the measurements so that I can compare the values with the real wavelength of sodium lamp (590nm) to see the validity of my experiment?I tried drawing the light source diagram

and came up with tan(α) = x/D but when I do that, the wavelength I get is really off the true wavelength of 590nm.

 

[member 553083]

1) When recording the slit width when the vertical wires just cease to be seen, you should take a very close look and try to record it as accurately as possible when the wires start to disappear. This might require some practice and patience but it will ensure that you get more accurate data.2) The vertical wires of the gauze disappear because the central maximum of the diffraction pattern coincides with the first minimum, causing the light sources between the wires to cancel each other out, making them appear hidden.3) To calculate the wavelength from your measurements, you can use the formula: Wavelength = (D x a)/x where D is the distance between the gauze and the telescope, a is the width of the slit, and x is the distance between the wires.By substituting in your values for D, a, and x, you should be able to get an estimate of the wavelength. You can then compare this to the true wavelength of the sodium lamp (590nm) to check the validity of your experiment.