Most Tested Topics in NEET (2019–2024)

1. Vernier Caliper / Screw Gauge Reading (Near-Annual) Questions provide a diagram or description showing MSR, coinciding VSD, and a zero error. The student must apply LC, compute raw reading, then apply zero error correction. The trap: confusing the direction of zero error correction. Drill rule: Positive zero error → subtract; Negative zero error → add.

2. Resonance Tube Calculation $\frac{1 Q}{year}$ Either: "Find speed of sound given $l_{1}$, $l_{2}$, f" (use v = 2f($l_{2}$−$l_{1}$)) or "Find end correction given $l_{1}$ and $l_{2}$" $\frac{use e = (l_{2}−3l_{1}}{2}$) or conceptual "Why is two-resonance formula preferred?" (end correction elimination). Always convert lengths to metres before substituting.

3. Metre Bridge (1 Q every 2 years) Either: find unknown S given R and balance length l, or find resistivity ρ given wire dimensions, or identify new balance after R-S interchange. Remember: l' = 100 − l after interchange.

4. Optics Sign Convention + Formula (1–2 Q/year) Concave mirror u-v calculation, convex lens image formation, or prism refractive index. The commonest error: using wrong sign for f or v. Memorize: concave mirror f negative, convex lens f positive.

5. Semiconductor I-V Characteristics $\frac{1 Q}{year}$ Identification of Si vs Ge from threshold voltage (0.7 vs 0.3 V), or Zener operation (reverse bias, constant voltage), or LED behavior (emits light in forward bias).

6. Graph Interpretation (1 Q every 2 years) $T^{2}$ vs l (slope = 4π^{2}/g), V-I (slope = R for ohmic), i-delta (U-curve, minimum at i = e), 1/v vs 1/u (intercepts = ±1/f).

Exam Strategy: Tackle Vernier/resonance tube questions first (formulaic, fastest marks). Optics sign convention takes time — read carefully. Semiconductor questions are often conceptual (threshold voltages are memorize-able).