Diffraction by single slit - effect of increasing the slit width

physicsilliterate

For diffraction by a single slit, what is the effect of increasing (a) the slit width, and (b) the wavelength? It was a problem on my daughter's final and I never seemed to be able to answer it for her. Related Introductory Physics Homework Help News on Phys.org

quasar987

Homework Helper
Gold Member
The answer lies in the fact that the minima are located at intervals of $n\lambda / D$ (value of sin)... so a bigger slit (D) makes narower maxima and a larger wavelenght ($\lambda$) makes wider maxima.

geosonel

physicsilliterate said:
For diffraction by a single slit, what is the effect of increasing (a) the slit width, and (b) the wavelength? It was a problem on my daughter's final and I never seemed to be able to answer it for her. for single-slit diffraction, the condition for MINIMUMs is:

$$y \ = \ \frac{m \lambda D}{s}$$

where y is the distance from central max to the m-th minimum of the diffraction pattern, m a positive integer, λ the wavelength, D the distance between single-slit and distant observation screen where diffraction pattern will be observed, and s the single-slit width. Thus:
a) increasing single-slit width will decrease width of central max ("shrink the diffraction pattern");
b) increasing wavelength will increase width of central max ("expand the diffraction pattern")

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