When red light passes through a dilute chlorophyll solution, the transmittance is approximately what range?

• A. 100%
• B. 50-75%
• C. Less than 25%
• D. None

Answer: (B)

Light that passes through a pigment depends on how much the pigment absorbs. Transmittance is the fraction of the incoming light that makes it through. Chlorophyll absorbs red light quite well, so red light isn’t transmitted freely. But when the solution is dilute, the amount of pigment is limited, so not all red photons are absorbed and a substantial portion still gets through. That combination—some absorption but not a lot due to low concentration—puts the transmittance in a mid-to-high range, typically around half to three-quarters of the incident red light. In terms of the underlying relation, if absorbance is small (which happens at low concentration), transmittance remains well below 100% but well above a very small value, aligning with about 50–75%.