Parameters
Wavelength λ
550 nm
Slit separation d
0.20 mm
Slit width a
40.0 μm
Screen distance L
1.00 m
Central max width: —
—
Fringe spacing Δy [mm]
—
1st max angle θ₁ [°]
—
Central max width [mm]
—
Resolving power R=mN
Theory
Double-slit interference (Young's experiment)
$$I(\theta)=I_0\cos^2\!\left(\frac{\pi d\sin\theta}{\lambda}\right)\cdot\text{sinc}^2\!\left(\frac{\pi a\sin\theta}{\lambda}\right)$$Bright fringes: $d\sin\theta = m\lambda \quad (m=0,\pm1,\pm2,\ldots)$
Dark fringes: $d\sin\theta = \left(m+\tfrac{1}{2}\right)\lambda$
Fringe spacing: $\Delta y = \dfrac{\lambda L}{d}$
Engineering applications: Diffraction-grating spectrometers for material analysis · CD/DVD optical storage · Photolithography resolution limits · Holographic interferometry for displacement measurement · X-ray diffraction (XRD) for crystal structure analysis (Bragg's law).