Monochromatic light that is incident normally is diffracted through 30 in the first order. Also notice that the maximum intensity of the double slit is 4 units, the 3-slit case has a maximum intensity of 9 units, and for 4-slits it is 16 units, as we expect when the amplitude increases by one unit with the addition of each slit. A diffraction grating 1.00cm wide has 10000 parallel slits. Notice that the bright fringes for any number of slits occur at the same places as for the double slit (provided they have the same slit separation), and that the number of dark fringes between bright fringes goes up by one every time another slit is added. (a) Find the angles for the first-order diffraction of the shortest and longest wavelengths of visible light (380 and 760 nm). Suppose you have one, and you send a beam of white light through it to a screen 2.00 m away. Diffraction gratings with 10,000 lines per centimetre are readily available. Putting these functions into a graphing calculator confirms what we found above, as well as what we suspect about \(n\) slits – that there are \(n-1\) dark fringes between each maximally-bright fringe.įigure 3.3.3 - Comparison of Interference Patterns by Number of Slits Example 1: Calculating Typical Diffraction Grating Effects.
