Which is/are the CORRECT option(s) that indicate(s) a multispectral sensor?
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A multispectral sensor has a small number of non-contiguous, moderately wide bands, unlike a hyperspectral sensor, which has hundreds of narrow contiguous bands, or a panchromatic sensor, which has just one band.
A sensor with 10 non-contiguous spectral bands having a bandwidth of about 0.04 μm
A sensor with 256 contiguous spectral bands with each having a bandwidth of 5 nm
A sensor with a single spectral band having a bandwidth of 0.4 μm
A sensor with 1000 contiguous spectral bands with each having a bandwidth of 1 nm
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The Correct Option isA
Solution and Explanation
Step 1: Set up the two distinguishing parameters. Any imaging sensor can be classified along two axes: the number of spectral bands $n$ it records, and whether those bands are contiguous (touching, so together they sample the spectrum almost continuously) or non-contiguous (separated by unused spectral gaps), together with the typical bandwidth $\Delta\lambda$ of each band.
Step 2: Place multispectral, hyperspectral and panchromatic sensors on this scale. Panchromatic sits at $n = 1$, one very wide band. Multispectral sits at roughly $n \approx 3$ to $20$, non-contiguous bands, with $\Delta\lambda$ typically tens of nanometers to a few tenths of a micrometer. Hyperspectral sits at $n$ in the hundreds, contiguous bands, with $\Delta\lambda$ of only a few nanometers to about ten nanometers, giving near continuous spectral coverage.
Step 3: Classify each option using this scale. (A): $n = 10$, non-contiguous, $\Delta\lambda = 0.04\ \mu m = 40\ nm$, this falls squarely in the multispectral range on all three counts. (B): $n = 256$, contiguous, $\Delta\lambda = 5\ nm$, both the large contiguous band count and the very narrow bandwidth place this in the hyperspectral range. (C): $n = 1$, $\Delta\lambda = 0.4\ \mu m$, a single band means this is panchromatic, since a sensor needs at least a handful of bands to be called multispectral. (D): $n = 1000$, contiguous, $\Delta\lambda = 1\ nm$, an extremely fine contiguous band set that is deep in hyperspectral (near ultraspectral) territory.
Step 4: Conclusion. Testing $n$, contiguity, and $\Delta\lambda$ together, only option (A) satisfies all three multispectral criteria simultaneously, so it alone is correct.
