Question

Remote sensing of vegetation characteristics is obtained by using
(A) UV rays
(B) Visible light
(C) Microwave
(D) Infrared rays
Choose the correct answer from the options given below :

• A. (A), (B) and (D) only.
• B. (A), (B) and (C) only.
• C. (A), (B), (C) and (D).
• D. (B), (C) and (D) only.

Hint:

The Normalized Difference Vegetation Index (NDVI) is calculated as: $\text{NDVI} = \frac{\text{NIR} - \text{Red}}{\text{NIR} + \text{Red}}$. It leverages the contrast between red absorption by chlorophyll and NIR reflectance by mesophyll cells to monitor vegetation health.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Vegetation displays unique spectral reflectance characteristics across different bands of the electromagnetic spectrum.
Remote sensing uses these spectral signatures to assess crop health, biomass, canopy structure, and water stress.

Step 3: Detailed Explanation:
Let us analyze how each radiation band interacts with plant canopies:
- (B) Visible light: Healthy green leaves contain chlorophyll pigments that absorb blue and red wavelengths of visible light for photosynthesis, while reflecting green light. Measuring visible light reflectance is essential for evaluating chlorophyll content and photosynthetic activity. (True)
- (D) Infrared rays: Healthy leaves have spongy mesophyll cells that strongly reflect Near-Infrared (NIR) radiation.
Comparing NIR reflectance with visible red reflectance is the basis for standard vegetation indices (like NDVI) used to assess crop vigor and biomass. (True)
- (C) Microwaves: Microwaves can penetrate cloud cover and vegetation canopies.
Radar backscatter measurements are highly sensitive to plant water content, leaf orientation, and woody biomass, making them valuable for assessing forest canopy structure and soil moisture beneath crop cover. (True)
- (A) UV rays: UV wavelengths are heavily scattered and absorbed by the Earth's atmosphere, and plants have protective surface waxes that absorb UV to prevent cell damage. As a result, UV radiation is not typically used for vegetative remote sensing.
Therefore, vegetation characteristics are monitored using Visible light (B), Microwaves (C), and Infrared rays (D).

Step 4: Final Answer:
The correct option is (B), (C), and (D) only, corresponding to option (D).