18 lessons
18 of 18 lessons by the NCERT chapter they teach from, in book order. The page is the first printed page of your NCERT book the lesson cites; PYQs are the past NEET questions on that topic.
6 questions from NEET 2020, 2021, 2025, 2026. Answers verified against NTA official keys.
By year in our set: 2020 (3) · 2021 (1) · 2025 (1) · 2026 (1)
Lesson: Experiment 13 Focal Length Parallax
Which of the following measurements require 'index correction' ?
Taking into account of the significant figures, what is the value of 9.99 m−0.0099 m ?
Lesson: Experiment 01 Vernier Calipers
Category: Overthinking
Reporting a measured length to more decimal places than the least count permits, e.g. writing 2.345 cm when LC = 0.01 cm.
Calculator output gives 4-5 decimals while the instrument's least count limits resolution to 2-3.
Round the final answer to the precision of the least-precise input or the limiting least count, whichever is coarser.
Lesson: Experiment 01 Vernier Calipers
Category: Sign Convention
When the jaws of a vernier/screw gauge close, the zero of the auxiliary scale may not coincide with the main-scale zero — this offset must be subtracted (positive zero error) or added back (negative zero error) from every reading.
Question gives a vernier/screw gauge reading along with a 'zero error' or 'when the jaws are closed the reading is...'.
Subtract positive zero error, add back negative zero error, BEFORE recording the corrected length.
Lesson: Experiment 13 Focal Length Parallax
Category: Graph Interpretation
Aligning the eye against the wrong reference point — e.g. against the back of an image pin instead of the tip — produces a parallax error even though the student thinks parallax was eliminated.
Optical bench / travelling-microscope reading where the eye reference is a different feature than the object reference.
Match the parallax-check reference: tip-to-tip, scratch-to-scratch, mark-to-mark — not tip-to-back.
Lesson: Experiment 01 Vernier Calipers
Root cause: concept gap
Always test for zero error by closing the jaws first; positive zero error is subtracted, negative is added back.
Lesson: Experiment 01 Vernier Calipers
Root cause: concept gap
Final reading precision = least count of the limiting instrument; do NOT carry extra digits from a calculator.
Lesson: Experiment 13 Focal Length Parallax
Root cause: concept gap
Move the eye laterally; if pointer and reflection move relative to each other, there is parallax. Adjust until they move together.
Lesson: Experiment 01 Vernier Calipers
Smallest length resolvable by a vernier; for standard 1-mm MSD with 10 VSD, LC = 0.1 mm = 0.01 cm.
| Symbol | Quantity | SI Unit |
|---|---|---|
| LC | least count | cm or mm |
| N | vernier divisions | - |
Lesson: Experiment 02 Screw Gauge
Smallest length resolvable by a screw gauge; typical pitch 0.5 mm, 50 head divisions ⇒ LC = 0.01 mm.
| Symbol | Quantity | SI Unit |
|---|---|---|
| p | pitch | mm |
| n_circ | circular divisions | - |
Lesson: Experiment 05 Young's Modulus
Combines fractional errors of independent measurements. Adds in absolute value (worst-case).
| Symbol | Quantity | SI Unit |
|---|---|---|
| Z | derived quantity | - |
| x_i | measured | - |
| n_i | exponent | - |
Unit-wide
wrong zero error direction
Sign convention is easily flipped.