1. Calculate Refractive Index ($\mu$):
$\mu = \frac{c}{v} = \frac{3 \times 10^8}{2 \times 10^8} = 1.5$.

2. Determine Radius of Curvature ($R$):
For a lens with radius of aperture $r = 3 \text{ cm}$ and thickness $t = 0.3 \text{ cm}$, the radius of curvature is given by $R \approx \frac{r^2}{2t}$ (for small thickness).
$R = \frac{3^2}{2 \times 0.3} = \frac{9}{0.6} = 15 \text{ cm}$.

3. Lens Maker's Formula:
$\frac{1}{f} = (\mu - 1) \left( \frac{1}{R_1} - \frac{1}{R_2} \right)$. For a plano-convex lens, $R_1 = R$ and $R_2 = \infty$.
$\frac{1}{f} = (1.5 - 1) \left( \frac{1}{15} \right) = 0.5 \times \frac{1}{15} = \frac{1}{30}$.
Thus, $f = 30 \text{ cm}$.

KCl must NEVER be administered via IV push — it can cause fatal cardiac arrest. During KCl infusion, the critical monitoring parameter is urine output (renal function).

Safe KCl infusion requires:

• Urine output \\geq 30 \\text{ mL/hr} — confirms kidneys can excrete excess potassium
• Urine output < 25–30 mL/hr indicates oliguria → STOP infusion immediately (risk of fatal hyperkalemia)
• Maximum peripheral infusion rate: 10 \\text{ mEq/hr}
• Maximum concentration peripherally: 40 mEq/L
• Never administer undiluted KCl

Signs of KCl toxicity/hyperkalemia: peaked T-waves, widened QRS, bradycardia, cardiac arrest. As a Charge Nurse, monitoring IV KCl infusions is a major patient safety responsibility.

Debridement is the removal of necrotic, devitalized, and contaminated tissue from a wound. It is essential for healing because:

• Necrotic tissue acts as a bacterial culture medium
• Devitalized tissue prevents granulation tissue formation
• Dead tissue impairs leukocyte migration (immune function)

Types of debridement:

Rewrite as $(A-\lambda I)X=0$. For non-trivial solutions, $\det(A-\lambda I)=0$.

$A = \begin{pmatrix}2&-2&1\\2&-3&2\\-1&2&0\end{pmatrix}$

The characteristic equation simplifies to $\lambda^3 + \lambda^2 - 5\lambda + 3 = 0$, which factors as $(\lambda-1)^2(\lambda+3)=0$.

Roots: $\lambda=1$ (repeated) and $\lambda=-3$. So the set contains exactly two elements: $\{1, -3\}$.

Zirconium (Zr, atomic number 40): [Kr] 5s² 4d². Mo: [Kr] 5s¹ 4d⁵ (exception); Se: [Ar] 3d¹⁰ 4s² 4p⁴; Sr: [Kr] 5s².