When an electromagnetic wave encounters the interface between two lossless homogeneous media with different refractive indices, part of the energy is reflected back and part is transmitted. What is this boundary interaction known as?

Introduction / Context:
At material interfaces, electromagnetic waves undergo reflection and transmission. The fractions of reflected and transmitted power depend on incidence angle, polarization, and refractive indices. These relations are foundational for optics, radar remote sensing, and radiative transfer.

Given Data / Assumptions:

• Two lossless homogeneous media with different refractive indices.
• Plane wave incidence at an arbitrary angle.
• Linear polarization states (s and p) may be considered.

Concept / Approach:
The Fresnel equations quantify reflection and transmission coefficients for s- and p-polarized waves at a planar boundary. While Snell’s law governs the change in propagation direction for the transmitted wave, the specific description of partial reflection and transmission magnitudes is encapsulated by Fresnel reflection/transmission.

Step-by-Step Solution:
Identify the phenomenon: simultaneous reflection and transmission at an interface.Associate to the proper formalism: Fresnel equations define the reflectance/transmittance.Select the term that directly names the reflective component: “Fresnel reflection.”

Verification / Alternative check:
Optics texts show how reflectance varies with incidence angle and polarization; at Brewster’s angle, p-polarized reflectance goes to zero, illustrating Fresnel behavior.

Why Other Options Are Wrong:

• Fresnel refraction describes the transmitted side, not the combined reflective phenomenon being asked.
• Snell’s law only gives refraction angles; it does not provide reflection coefficients.
• “None of these” ignores standard terminology.

Common Pitfalls:
Confusing direction (Snell) with amplitude/energy (Fresnel); forgetting polarization dependence.

Final Answer:
Fresnel reflection