Agricultural Physics- ICAR JRF/SRF 2024

• Optical Filters in Remote Sensing:
• short-pass filter (also termed a high-frequency / short-wavelength pass filter) transmits electromagnetic radiation at wavelengths shorter than a specified cut-off point while rejecting longer wavelengths. (Correct answer: Option 4)

• Step 1: Ground Scale Conversion:

$$\text{Photo scale} = 1 : 10,000 \implies 1\text{ cm on photo} = 10,000\text{ cm} = 100\text{ m on ground}$$ $$1\text{ cm}^2\text{ on photo} = 100\text{ m} \times 100\text{ m} = 10,000\text{ m}^2 = 1.0\text{ hectare}$$

• Step 2: Area Represented by a Single Dot:

$$\text{Grid density} = 20\text{ dots/cm}^2$$ $$\text{Area per dot} = \frac{1.0\text{ ha}}{20\text{ dots}} = 0.05\text{ ha/dot}$$

• Step 3: Total Flooded Ground Area:

$$\text{Total Area} = 120\text{ dots} \times 0.05\text{ ha/dot} = 6.0\text{ hectares}$$

• Conclusion: The flooded ground area is 6 ha. (Correct answer: Option 2)

• Blackbody Thermal Radiation Principles:
• By definition, an ideal blackbody has an emissivity of unity across all wavelengths:

$$\epsilon = 1.0$$

• Radiant temperature ($T_{\text{rad}}$) and kinetic temperature ($T_{\text{kin}}$) are related by Stefan-Boltzmann's law:

$$T_{\text{rad}} = \epsilon^{1/4} \cdot T_{\text{kin}} = (1.0)^{1/4} \cdot T_{\text{kin}} = T_{\text{kin}}$$

• Conclusion: If kinetic temperature is 27.0 °C, the radiant temperature of the blackbody is exactly 27.0 °C. (Correct answer: Option 1)

• AVIRIS Remote Sensing Sensor:
• NASA Jet Propulsion Laboratory (JPL) airborne hyperspectral imaging sensor.
• Acronym stands for Airborne Visible-Infrared Imaging Spectrometer, which records 224 contiguous spectral channels from 380 nm to 2500 nm. (Correct answer: Option 2)