# Wave nature of light problem

Given a wavelength length $$\alpha$$, what is the maximum Width (D) of a single slit, which would have no diffraction minima?

It seems like a proof problem to me and I am trying to get a head start.
should I use $$D * sin (\theta) = m \alpha$$ ?

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OlderDan
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leolaw said:
Given a wavelength length $$\alpha$$, what is the maximum Width (D) of a single slit, which would have no diffraction minima?

It seems like a proof problem to me and I am trying to get a head start.
should I use $$D * sin (\theta) = m \alpha$$ ?
Yes, that and what you know about the sine function.

that sin of zero degrees is 0

OlderDan
Yes, but at zero degrees you will never have a minimum. From the geometry of the single slit diffraction setup, to not find any minima after the slit, the angle $\theta$ would have to be 90 degrees for the first minimum. So then what does
$$D * sin (\theta) = m \alpha$$
I see, so $$D sin (90) = (1) \alpha$$, which is the first minimum, and D has to be equal to the wavelength $$\alpha$$.