Diffraction of light into a spectrum via a CD/DVD

The Science

When we put a CD in a dark room and set the flashlight on a specific angle, we can see rainbow pattern or rays on the surface of the CD. A CD’s surface is not smooth, it consists of thousands of tiny tightly packed spiral tracks which are used to store data inside the CD. When light hits these grooves, instead of bouncing off in a single direction, it splits up. This is because white light is a mixture of different colours (red, orange, yellow, green, blue, voilet and indigo). Each colour has a bit different wavelength. When light hits these tiny grooves, it bends by a slightly different angle for each wave length (this is called diffraction). This is why we see patterns or rays of the colours, that come together to form the white light.

Why I Chose It

I play console games alot and whenever I used to pull out a game CD, rainbowed colours used to appear on its surface (like a blend, not like the rays in my picture because in that photo, The light source has been set closer and at a specific angle), so I used to wonder why it happens. Thatswhy, this contest seemed a great opportunity to do some research on it abd let others know about this aswell.

Muhammad Abdullah Verified Volunteer

Volunteer · Maker · Lahore · Member since Jun 2026