Diffraction Gratings

Rainbows from a CD

An interactive lesson with 7 steps, about 6 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Grating equation: $d\sin\theta = m\lambda$.
• Gratings split light into sharp spectra; CDs act as gratings.
• Spectral lines identify elements, even in distant stars.

Steps

1. Thousands of slits
2. Adding eight arrows
3. CD rainbow
4. How many orders?
5. Split the sodium lines
6. First-order angle
7. Fingerprints of elements