What measurement allows determination of an element's relative amount in a sample?

• A. The color of the sample
• B. The density of the sample
• C. The intensity of the characteristic x-rays
• D. The sample’s temperature

Answer: (C)

In XRF analysis, you determine how much of an element is in a sample by looking at how many of its characteristic X-rays are emitted and detected when the sample is irradiated. The intensity (or peak area) of those specific X-ray lines is proportional to the element’s concentration, especially after proper calibration and corrections for the sample matrix and instrument response. The other options don’t reflect a direct, element-specific signal: color isn’t a reliable quantitative indicator of composition; density is a bulk property that doesn’t reveal which elements are present; and temperature doesn’t indicate elemental abundance.