Significant Figures
How many significant figures are present in the carefully recorded experimental measurement written as 0.00408000 metre by a student?
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About This Question
- Subject
- physics
- Chapter
- physics and measurement
- Topic
- significant figures
- Difficulty
- Easy
- Year
- 2025
Solution
Correct Answer:
6
Significant figures convey the precision of a measured value, and a clear set of rules decides which digits count. Leading zeros that merely fix the position of the decimal point are never significant, so the three zeros in 0.00 before the 4 are placeholders and contribute nothing. The non-zero digits 4 and 8 are always significant, and the zero sandwiched between them is also significant because trapped zeros count. Crucially, trailing zeros that appear after a decimal point are significant, since a careful experimenter writes them only to indicate measured precision. Therefore the digits 4, 0, 8, 0, 0, 0 are all significant, giving a total of six. The choice 3 wrongly ignores the meaningful trailing zeros, while 5 drops exactly one of them. The choice 8 incorrectly counts the leading placeholder zeros as well. This matches the NCERT rules for significant figures used throughout measurement chapters. A plausibility check helps: rewriting the value in scientific notation as 4.08000 × 10^-3 displays exactly six significant digits, confirming the answer.
This easy difficulty physics question is from the chapter physics and measurement, covering the topic of significant figures. It appeared in the 2025 exam.
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