The transmitted radiation through a sample can be less than the incident energy due to several factors:
Absorption: The sample material can absorb a portion of the incident radiation energy. Absorption occurs when the energy of the incident photons is transferred to the atoms or molecules of the material, causing them to undergo electronic transitions or other energy-absorbing processes. This absorbed energy is not re-emitted as transmitted radiation, resulting in a reduction in the transmitted energy.
Scattering: Scattering refers to the redirection of radiation in different directions when it interacts with particles or irregularities within the sample. Scattering can cause a portion of the incident radiation to be scattered in different directions rather than being transmitted through the sample. This scattered radiation does not contribute to the transmitted energy.
Reflection: Some portion of the incident radiation can be reflected back from the surface of the sample. Reflection occurs when the incident radiation encounters a boundary between two different media with different refractive indices. The reflected radiation is not transmitted through the sample and thus does not contribute to the transmitted energy.
Geometric factors: The geometry of the sample and the size of the detector can also affect the measured transmitted energy. If the sample is not completely transparent or the detector does not capture all transmitted radiation, some energy may be lost or not accounted for in the measurement.
These factors can lead to a reduction in the transmitted energy compared to the incident energy when radiation passes through a sample. The extent of the reduction depends on the properties of the sample, such as its composition, thickness, and optical properties, as well as the characteristics of the incident radiation.