Question

Which of the following statement(s) is/are CORRECT?

• A. In optical remote sensing, more often we are interested in diffuse reflections
• B. The reflection will be diffuse if the incident wavelength is comparatively much larger than the surface roughness
• C. A surface that reflects microwave in specular manner may reflect the visible in diffuse manner
• D. All wavelengths emitted by the Sun reflect in diffuse manner from the objects on the surface of the Earth

Hint:

“Smooth vs. rough” is {relative} to wavelength: $\lambda \gg h ⇒$ specular; $\lambda \sim h$ or $< h ⇒$ diffuse. Thus the same surface can behave differently across spectral regions.

Answer 1

The Correct Option is A

(A) True. For most land-surface studies (vegetation, soils), we rely on diffuse (Lambertian-like) reflection to infer material properties.
(B) False. If the wavelength $\lambda$ is much larger than the height of surface irregularities ($\lambda \gg h$), the surface appears optically smooth, leading to specular, not diffuse, reflection. Diffuse scattering occurs when roughness is comparable to or larger than the wavelength.
(C) True. Microwave wavelengths (cm–mm) are far longer than visible (400–700 nm). A surface may be smooth for microwaves (specular) yet rough for visible (diffuse).
(D) False. Earth surfaces can reflect specularly (e.g., sunglint from water, polished metal); not all wavelengths are reflected diffusely.