UPSC Prelims 2011 Q69: Science & Technology – Computer & Information Technology
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 is 1.2 mm.
Which of the statements given above is/are correct?
- (a) 1 only
- (b) 1 and 2 only
- (c) 2 and 3 only
- (d) 1, 2 and 3
Answer: (b) 1 and 2 only
Explanation
Blu-ray Disc vs DVD: checking the three statements
Blu-ray Disc (BD) is a newer optical disc format offering major upgrades over DVD.
| Statement | Verdict | Reason |
|---|---|---|
| 1. DVD supports SD video, BD supports HD video | Correct | This is the primary distinguishing feature of Blu-ray over DVD |
| 2. BD has several times more storage capacity than DVD | Correct | A single-layer BD holds ~25 GB, versus a DVD's ~4.7 GB — several times more |
| 3. BD thickness is 2.4mm, DVD is 1.2mm | Incorrect | Both BD and DVD discs are the same physical thickness (1.2mm); only the internal data layer depth differs |
Blu-ray vs DVD:
| Point | DVD | Blu-ray |
|---|---|---|
| Video quality | Standard Definition | High Definition |
| Storage | ~4.7 GB | ~25 GB+ |
| Physical thickness | 1.2 mm | 1.2 mm (same) |
Answer: (b) 1 and 2 only.
Why each option is right or wrong
- (a) Incorrect. Statement 2 (greater storage capacity) is also correct, so '1 only' is incomplete.
- (b) CORRECT. The HD-vs-SD video support and the much larger storage capacity are both accurate; the thickness claim in statement 3 is false.
- (c) Incorrect. Statement 1 (HD vs SD support) is also correct; and statement 3's thickness claim is wrong, so this combination fails.
- (d) Incorrect. Statement 3's thickness claim is false — both discs are the same 1.2mm thickness — so 'all three' cannot be correct.
Key point
Blu-ray beats DVD in video quality (HD vs SD) and storage capacity (far more GB) — but both discs share the SAME 1.2mm physical thickness; statement 3's claim of different thickness is false.
Remember
Blu-ray vs DVD: HD vs SD video, much larger storage — but SAME 1.2mm disc thickness.
Common mistakes
- Assuming Blu-ray discs are physically thicker than DVDs — they are not.
- Underestimating just how much more storage Blu-ray offers over DVD.
- Missing the core HD vs SD distinction as the headline difference.
Exam tip
Blu-ray and DVD are the same physical thickness (1.2mm); the real differences are video resolution support and storage capacity.
Sources
- Blu-ray Disc Association — White Paper: Blu-ray Disc Format, 1. General
- DVD Forum — DVD Specifications for Read-Only Disc (Book A)