Suppose we have two slits and light (modelled here as a longitudinal wave) is coming out from the slits radially. The waves can interfere with one another constructively or destructively. The points which are constructive are observed as bright spots (maxima) while the points which are destructive are observed as dark spots (minima) on the screen.
Important formulae: d sin θ = mλ --> sin θ = mλ/d tan θ = (Y_m)/L Where: d is distance b/w slits m is order Y is distance b/w maximas θ is angle b/w maximas L is distance b/w double slit and screen Questions: 1) What happens when 'd' is increased? 2) What happens when wavelength, λ, is increased? (play around with the period slider. Remember that larger period gives larger wavelength) 3) Why is the central maxima (m_0) brighter than the 3rd order maxima (m_3)? Other notes: The max number of diffraction bands is given by: m=d/λ Useful Youtube videos: https://youtu.be/OOgPYR1OvjY https://youtu.be/cUmIL2hbgR4
