Electromagnetic Waves – What are they characterised by? In physics and remote sensing, electromagnetic waves (for example, radio, microwave, infrared, visible light) are described by multiple measurable attributes. Which of the following collectively characterise an electromagnetic wave and how it appears to a sensor or observer?

Introduction / Context:
Electromagnetic (EM) waves are the backbone of communication, imaging, and remote sensing. Properly describing an EM wave means accounting for how often the fields oscillate, how long each cycle is in space, how much power the wave carries, and the geometric orientation in which it propagates, including its polarization state.

Given Data / Assumptions:

• The discussion applies to free-space propagation and common media.
• Quantities follow standard radiometric and wave definitions.
• Linear, time-harmonic fields for simplicity.

Concept / Approach:

An EM wave can be specified by frequency f and wavelength lambda, related by c = f * lambda in free space. Intensity (or irradiance) captures power per unit area, which links to what detectors measure. The direction of travel defines the propagation vector, while polarization specifies the orientation and evolution of the electric field vector, crucial for target/material interactions and antenna/sensor design.

Step-by-Step Solution:

Verification / Alternative check:

Remote sensing metadata and communication standards specify center frequency, bandwidth, polarization, look direction, and radiometric calibration, confirming the multi-attribute characterization.

Why Other Options Are Wrong:

Choosing only one attribute omits essential wave properties; sensors and analyses require all.

Common Pitfalls:

Confusing intensity with radiance/irradiance; assuming polarization is unimportant outside radar—it also matters in optics.

Final Answer:

All of these