Question

The spectral reflectance curves of three materials (A, B, and C) are shown, along with three wavelength bands X, Y, Z. Which of the following statement(s) is/are CORRECT?

• A. Each of the curve is the spectral signature of the respective material
• B. A sensor designed for the wavelength band ‘Y’ will best distinguish these materials in the image captured by the sensor
• C. A sensor designed for the wavelength band ‘Z’ will best distinguish these materials in the image captured by the sensor
• D. These curves are normally produced using a spectro-radiometer

Hint:

For material discrimination, pick bands where class reflectances are maximally separated and intra-class variance is small—often identified directly from spectral signature plots.

Answer 1

The Correct Option is A

(A) True. A plot of reflectance versus wavelength for a material is its spectral signature.
(B) True. From the figure, the separation between the reflectances of A, B, C is largest around band Y; hence a band centered at Y provides the best class separability.
(C) False. Around band Z, two of the materials have similar reflectance (curves nearly intersect), yielding poor separability compared to Y.
(D) True. Spectral signatures are typically measured in the field/lab using a spectro-radiometer (or field spectrometer).