In normal incidence, if the impedance of medium 2 equals that of medium 1, what happens to the intensity?

• A. 100% of the intensity will be reflected
• B. 100% of the intensity will be transmitted
• C. The reflection and transmission coefficients will be equal
• D. The answer cannot be determined without values given

Answer: (B)

When light or any wave travels from one medium to another and hits the boundary between the two at normal incidence, the behavior of the intensity of the wave is influenced by the impedance of the two media. Impedance is a measure of how much resistance a wave encounters as it travels through a medium.

If the impedance of medium 2 is equal to that of medium 1, it means that the wave encounters no change in resistance as it moves from the first medium to the second. In this scenario, there is no barrier to the transmission of the wave, resulting in the wave continuing into the new medium without any reflection.

Therefore, 100% of the intensity will be transmitted into the second medium. In contrast, if the impedances were mismatched, some portion of the intensity would be reflected back into the first medium. In this case, since there is an equal impedance, reflection does not occur, and all the intensity is transmitted, confirming that the correct answer is that 100% of the intensity will be transmitted.