Short Question Asso Leg poly_Orthogonal ppt
3 Marks
Short Question: Orthogonality of Associated Legendre Polynomials
Question (3 Marks)
State the orthogonality property of associated Legendre polynomials \(P_\ell^{\,m}(x)\) for fixed \(m\) on the interval \([-1,1]\).
\[
\text{(Write the standard relation and define } \delta_{\ell n}\text{.)}
\]
Expected Answer (Brief)
\[
\boxed{
\int_{-1}^{1} P_\ell^{\,m}(x)\,P_n^{\,m}(x)\,dx
=
\frac{2}{2\ell+1}\,\frac{(\ell+m)!}{(\ell-m)!}\,\delta_{\ell n}
}
\]
where \(\delta_{\ell n}=1\) if \(\ell=n\) and \(0\) if \(\ell\neq n\).
Scheme of Evaluation
Marking Scheme (Total: 3 Marks)
| What the student should write | Marks |
|---|---|
| Writes the correct orthogonality statement in integral form (must include limits \(-1\) to \(1\)). | 1.5 |
| Correct normalization factor (must have factorial ratio \(\dfrac{(\ell+m)!}{(\ell-m)!}\) and \(\dfrac{2}{2\ell+1}\)). | 1.0 |
| Correct meaning of \(\delta_{\ell n}\) (Kronecker delta) OR clearly states “integral is zero for \(\ell\neq n\)”. | 0.5 |
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