Question

When the sensor detects EMR at an object and detects the amount of that energy which is reflected back, it is:

• A. Passive sensing
• B. Active sensing
• C. Direct sensing
• D. Indirect sensing

Hint:

Passive sensing uses naturally reflected or emitted radiation, while active sensing sends its own energy.

Answer 1

The Correct Option is A

Concept:
Remote sensing may be active or passive depending on the source of electromagnetic radiation.

Step 1: Passive sensing.
Passive sensors detect naturally available radiation reflected or emitted by objects. \[ \text{Passive sensing}=\text{detects reflected natural EMR} \]

Step 2: Active sensing.
Active sensors send their own energy towards the object and then measure the returned signal. \[ \text{Active sensing}=\text{sensor provides its own energy} \]

Step 3: Apply the statement.
The question says the sensor detects EMR reflected back from the object. This matches passive sensing. \[ \therefore \text{Correct Answer is (A)} \]