UPSC Prelims 2008 Q112: Science & Technology – Physics
Consider the following statements:
1. A widely used musical scale called diatonic scale has seven frequencies.
2. The frequency of the note Sa (स) is 256 Hz and that of Ni (नी) is 512 Hz.
Which of the statements given above is/are correct?
- (a) 1 only
- (b) 2 only
- (c) Both 1 and 2
- (d) Neither 1 nor 2
Answer: (a) 1 only
Explanation
Checking two claims about musical scale frequencies
These statements examine the structure of the diatonic musical scale and the specific frequencies of Indian classical notes.
| Statement | Verdict | Reason |
|---|---|---|
| 1. The diatonic scale has seven frequencies | Correct | The diatonic scale is indeed built from seven distinct notes/frequencies per octave |
| 2. Sa is 256 Hz, Ni is 512 Hz | Incorrect | If Sa is 256 Hz, the note at 512 Hz would actually be the upper octave Sa (double the frequency), NOT Ni — Ni, being the note just below the upper Sa, should have a frequency somewhat less than 512 Hz |
Correcting the frequency claim:
| Point | Detail |
|---|---|
| Sa | 256 Hz |
| 512 Hz | Actually the upper octave Sa (double frequency), NOT Ni |
Answer: (a) 1 only.
Why each option is right or wrong
- (a) CORRECT. The seven-frequency diatonic scale claim is accurate; the specific Ni frequency claim is incorrect.
- (b) Incorrect. Statement 2's Ni frequency claim is false, so '2 only' is wrong.
- (c) Incorrect. Statement 2 is inaccurate, so 'both' cannot be correct.
- (d) Incorrect. Statement 1 is accurate, so 'neither' is wrong.
Key point
The diatonic scale genuinely has seven frequencies — but if Sa is 256 Hz, 512 Hz represents the UPPER OCTAVE SA (double frequency), not Ni, which should be a note just below that.
Remember
The diatonic scale has seven frequencies — but 512 Hz (double 256 Hz) represents the upper octave Sa, not Ni.
Common mistakes
- Confusing the upper octave Sa (double frequency) with the note Ni, which comes just before it in the scale.
- Not understanding the octave-doubling principle in musical frequency relationships.
- Assuming both parts of a two-statement question must share the same truth value.
Exam tip
Doubling a note's frequency gives its own note an octave higher (Sa → upper Sa), not a different note (Ni). A key music-physics distinction.
Sources
- NCERT Class XI Physics — Waves (musical sounds and frequency)
- Encyclopaedia Britannica — diatonic scale