A new optical disc format known as the Blu-ray Disc (BD) is becoming popular. In what way is it different from the traditional DVD? 1) DVD supports Standard Definition video while BD supports High Definition video. 2) Compared to a DVD, the BD format has several times more storage capacity. 3) Thickness of BD is 2.4 mm while that of DVD is1.2 mm. Which of the statements given above is/are correct?

The correct answer is B (1 and 2 only). Statements 1 and 2 are true, and Statement 3 is false.

• Statement 1 is correct. DVD is built for Standard Definition (around 480p in the common format), while Blu-ray is designed for High Definition (720p and 1080p), and the difference comes from the laser wavelength and the data density it allows.
• Statement 2 is correct. A single-layer DVD holds about 4.7 GB, while a single-layer Blu-ray holds about 25 GB, roughly five times more. The gap comes from the shorter 405 nm blue-violet laser, which focuses to a smaller spot than the 650 nm red laser in DVD.
• Statement 3 is wrong. Both discs are 1.2 mm thick. The 1.2 mm standard is shared so that the same drive mechanics can handle both formats. The protective layer on Blu-ray is thinner, about 0.1 mm, which is what allows the tighter focus.

The core concept is optical storage and how laser wavelength determines data density. This links to the Mains digital-infrastructure and technology-diffusion themes, where format wars and backward compatibility are common discussion points.

Trap: candidates see that the thickness figures differ in the protective layer or the disc is thicker in their memory, and they mark Statement 3 as correct. Both discs measure 1.2 mm overall.