​In remote sensing, which one of the following formulae is used for the calculation of normalized difference vegetation index (NDVI)?​

Correct option is D

Explanation-

NDVI (Normalized Difference Vegetation Index) is a widely used remote sensing index to assess vegetation health and cover using satellite imagery. It compares the reflectance of red light (RED) and near-infrared light (NIR) from the Earth's surface.

The correct formula for calculating Normalized Difference Vegetation Index (NDVI) is:

$$\text{NDVI} = \frac{\text{NIR} - \text{RED}}{\text{NIR} + \text{RED}}$$​​

NIR: Near-Infrared reflectance (plants reflect strongly in this region)
RED: Red reflectance (plants absorb strongly in this region)

Numerator:
NIR − RED → measures difference in reflectance
Denominator:
NIR + RED → normalizes the value to keep NDVI between -1 and +1

Healthy vegetation: reflects more NIR and absorbs RED, giving high NDVI values (close to +1)
Bare soil or unhealthy vegetation: reflect similar amounts of NIR and RED, giving values near 0
Water or built-up areas: can produce negative values.

So, the correct answer is option d - (NIR - RED) / (NIR + RED)