Index matching gel reduces Fresnel reflection.

Index matching gel reduces Fresnel reflection.

• A. True
• B. False
• C. Not sure
• D. Both

Answer: (A)

The effect being tested is that reducing the mismatch of refractive indices at an interface lowers Fresnel reflections. Light reflecting at a boundary depends on how different the refractive indices of the two materials are; the larger the mismatch, the more light bounces back. An index matching gel sits between the two media and has a refractive index closer to both, smoothing the transition. This reduces the reflectance described by the simple normal-incidence formula R ≈ ((n1 − n2)/(n1 + n2))^2, so less light is reflected and more is transmitted. That’s why using an index matching gel decreases Fresnel reflections at that interface. If there were no gel or a bigger mismatch (like air in the gap), more reflection would occur. The statement is true.

The effect being tested is that reducing the mismatch of refractive indices at an interface lowers Fresnel reflections. Light reflecting at a boundary depends on how different the refractive indices of the two materials are; the larger the mismatch, the more light bounces back. An index matching gel sits between the two media and has a refractive index closer to both, smoothing the transition. This reduces the reflectance described by the simple normal-incidence formula R ≈ ((n1 − n2)/(n1 + n2))^2, so less light is reflected and more is transmitted. That’s why using an index matching gel decreases Fresnel reflections at that interface. If there were no gel or a bigger mismatch (like air in the gap), more reflection would occur. The statement is true.