Monochromatic light hits a grating and fans into ordered bright fringes at d sin(angle) = n·(wavelength). Drag the sliders to move the orders, sharpen them with more slits, and spread them on the screen.
First-order angle d sin = 1·wavelength
15.96°
7 bright fringes: orders up to n = 3 emerge on each side.
Grating numbers
Slit spacing d2.00 µm
Highest order nmax3
Bright fringes (2nmax+1)7
First order on screen28.6 cm
Wavelength550 nm
Line density500 /mm
Number of slits N6
Screen distance D100 cm
d = 1/(lines per metre) · orders exist only while n·(wavelength)/d ≤ 1 · screen trace spans ±150 cm and uses the N-slit intensity, so more slits means sharper maxima at the same angles.
Tip: push the line density up and watch the orders spread apart while the highest order drops — then add slits and see each bright fringe turn needle-sharp.