Remote sensing sensors are built to pick up specific slices of the electromagnetic spectrum, and each slice has a name tied to its wavelength range. Sorting visible light, near infrared, thermal infrared and microwave radiation by wavelength is really just a matter of knowing roughly where each band sits on the spectrum.
- Visible: about $0.4$ to $0.7$ micrometres, the same narrow band the human eye detects, and the shortest wavelength band among the four.
- Near Infrared: about $0.7$ to $1.3$ micrometres, just past red light, still close in scale to visible light but slightly longer.
- Thermal Infrared: roughly $3$ to $14$ micrometres, linked to heat emitted by the Earth's surface itself rather than reflected sunlight, so its wavelength is several times longer than near infrared.
- Microwave: from about $1$ millimetre up to $1$ metre, thousands of times longer than thermal infrared, which is why microwave and radar sensors can pass through clouds and rain that block the shorter optical and infrared bands.
Lining these four ranges up from shortest to longest wavelength gives Visible, then Near Infrared, then Thermal Infrared, then Microwave, exactly the sequence in option (A). Option (B) wrongly starts with thermal infrared, option (C) wrongly starts with microwave (the longest band, not the shortest), and option (D) wrongly ends with visible (the shortest band, which should come first), so none of these three match the true wavelength order.
Let's summarize:
- Wavelength increases in this order: visible, near infrared, thermal infrared, microwave.
- Longer wavelength bands like microwave penetrate cloud and haze better than the shorter optical and infrared bands.
So the correct increasing wavelength order is Visible, Near Infrared, Thermal Infrared, Microwave, option (A).