Estimate diffraction angle - homemade spectrometer

[Jon.G]

Homework Statement

Estimate the diffraction angle.
The spectrometer is made from rolling up a 30cm long piece of cardboard into a tube. Duct tape is placed over one end, and a thin slit is made. The other end has a diffraction grating held in place.
I look through the diffraction grating and can see the slit and 8 spectra, going away from the slit. (as if there's one at each corner and halfway along each side of a square)

Homework Equations

ΔΘ=2λ/b for b>>λ
b is slit width

The Attempt at a Solution

I'm not sure if there's another way to do this.
Using this equation, I'd just be taking estimates that could be way off for the slit width and the wavelength (just using white light).
But then the task does say to estimate, so it could be ok.

Thanks for your time.

 

[mfb]

If your diffraction grating has slits, I don't see how you get the pattern you described.
Are you sure that you looking through the tube is the intended way to use the spectrometer?

 

[BvU]

Does your spectrometer look something like the one described here ?