An engineering team is designing a nondestructive inspection system for composite aircraft panels that may contain multiple hidden defects such as surface scratches, subsurface delaminations, and deeply embedded moisture pockets. The team can incorporate four different illumination sources: microwave (λ≈3cm), infrared (λ≈10μm), visible (λ≈550nm), and ultraviolet (λ≈200nm).
(a) For each of the four wavelengths provided, calculate the corresponding frequency. Present your answers in appropriate SI units.
(b) For each type of potential defect listed, select the illumination source that is most likely to reveal the defect clearly. Justify each selection by referring to the interaction of electromagnetic waves with matter (for example, penetration depth, scattering, or absorption).
(c) Discuss the trade-off between spatial resolution and penetration depth as wavelength decreases across the electromagnetic spectrum. Support your discussion with at least one quantitative comparison drawn from the values in part (a).
(d) Recommend an optimal two-band configuration (choose any two of the four sources) that balances comprehensive defect detection with practical system complexity. Defend your recommendation with reference to your analysis in parts (b) and (c).