Unit 2

• Precipitation Mechanisms in Clouds:
• Warm Clouds (Temperature $\gt 0^\circ\text{C}$ throughout): Completely lack ice crystals; rainfall is generated exclusively via the Collision-Coalescence theory (Bowen & Langmuir), where larger droplets falling faster sweep up and coalesce with smaller droplets.
• Cold Clouds: Rain develops via the Bergeron-Findeisen ice crystal process. (Correct answer: Option 1)

• Short Day Plants $\rightarrow$ (IV) Rice: Rice (Oryza sativa) initiates floral induction only when the photoperiod is shorter than its critical day length.
• Long Day Plants $\rightarrow$ (I) Wheat: Wheat (Triticum aestivum) requires photoperiods longer than its critical day length to transition from vegetative growth to heading and flowering.
• Day Neutral Plants $\rightarrow$ (II) Tomato: Tomato (Solanum lycopersicum) flowers regardless of day length, controlled primarily by physiological node number and vegetative vigor.
• Intermediate Plants $\rightarrow$ (III) Andropogon: Andropogon scoparius requires an intermediate photoperiod window (neither too long nor too short) to initiate flowering.

Correct option: (4) (A) - (IV), (B) - (), (C) - (I), (D) - (ttl)

• Specific Surface Area of Sand:
• Specific surface area ($S_w$) is inversely proportional to particle diameter ($S_w = \frac{6}{\rho \cdot d}$).
• Coarse sand grains ($0.05 - 2.0\text{ mm}$) have very small surface areas per unit mass, typically $\lt 2\text{ m}^2/\text{g}$ (often $0.01 - 0.1\text{ m}^2/\text{g}$), compared to $10 - 40\text{ m}^2/\text{g}$ for illite and up to $800\text{ m}^2/\text{g}$ for smectite clay. (Correct answer: Option 2)