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"What is an easy way to determine if a disc is a CD or DVD just by looking at it?"

The edge of a DVD typically has a distinct purple hue or iridescent effect when viewed from the bottom, whereas CDs have a green or green/gold hue.

DVDs are made of two sheets of polycarbonate sandwiching the recording layer, which is visible as a thin trench down the middle of the disc when viewed from the edge.

CDs usually have a more matte finish compared to DVDs, which have a more mirrored appearance, with reflectivity levels of around 60-70% for CDs and 90-95% for DVDs.

If you hold a disc at an angle, you can see a rainbow of colors reflected off the surface, which is due to the principle of diffraction, where light bends around the tiny obstacles on the disc.

The color of the disc can also give it away: CDs tend to have a green or green/gold hue, while DVDs often have a purple or silver color.

The label on the disc can also be a giveaway, with CDs often labeled as "Compact Disc" and DVDs featuring a simplified image of a disc.

If you can't see any labels or symbols, you can try tapping the disc gently against a surface - DVDs tend to have a distinct sound or feel compared to CDs.

DVDs often have a more rounded edge compared to CDs, which can be more angular.

The reflective surface of a DVD can create a "ringing" effect when tilted at certain angles, which is not typically seen on CDs.

Some DVDs may have a small hole or pit on the underside, which can be visible when held up to light.

CDs tend to be more prone to scratches and marks due to their thinner protective layer, whereas DVDs have a thicker layer that makes them more resistant to damage.

If you look closely at the center hole of the disc, you may be able to see the "land" or raised area around the hole, which is typically more prominent on DVDs.

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