---
title: "A student investigates the spectroscopic properties of an aqueous solution of a food dye. The student collects the absorbance spectrum shown below across the visible wavelength range from \\(400\\text{ nm}\\) to \\(700\\text{ nm}\\).  | Wavelength range (\\(\\text{nm}\\)) | Color of light | |—|—| | \\(400 – 480\\) | Blue / Violet | | \\(480 – 560\\) | Green | | \\(560 – 640\\) | Orange / Yellow | | \\(640 – 700\\) | Red |  Based on the spectrum and the table, which of the following identifies the optimal wavelength to construct a Beer’s law calibration curve for this dye, and correctly explains the perceived macroscopic color of the solution?"
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url: "https://nerd-notes.com/ubq/123723/"
date_modified: "2026-09-28T12:02:10+00:00"
---

# A student investigates the spectroscopic properties of an aqueous solution of a food dye. The student collects the absorbance spectrum shown below across the visible wavelength range from \(400\text{ nm}\) to \(700\text{ nm}\).

| Wavelength range (\(\text{nm}\)) | Color of light |
|—|—|
| \(400 – 480\) | Blue / Violet |
| \(480 – 560\) | Green |
| \(560 – 640\) | Orange / Yellow |
| \(640 – 700\) | Red |

Based on the spectrum and the table, which of the following identifies the optimal wavelength to construct a Beer’s law calibration curve for this dye, and correctly explains the perceived macroscopic color of the solution?

A student investigates the spectroscopic properties of an aqueous solution of a food dye. The student collects the absorbance spectrum shown below across the visible wavelength range from \(400\text{ nm}\) to \(700\text{ nm}\).

| Wavelength range (\(\text{nm}\)) | Color of light |
|---|---|
| \(400 - 480\) | Blue / Violet |
| \(480 - 560\) | Green |
| \(560 - 640\) | Orange / Yellow |
| \(640 - 700\) | Red |

Based on the spectrum and the table, which of the following identifies the optimal wavelength to construct a Beer's law calibration curve for this dye, and correctly explains the perceived macroscopic color of the solution?

![A grayscale line graph plotting Absorbance on the vertical y-axis versus Wavelength in nanometers on the horizontal x-axis. The y-axis runs from 0.0 to 1.0 with labeled tick marks at 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0. The x-axis runs from 400 to 700 with labeled tick marks at 400, 450, 500, 550, 600, 650, and 700. A single solid black curve is shown. Starting at an absorbance of 0.05 at 400 nm, the curve dips to a minimum near 0.02 between 430 nm and 450 nm, rises gradually past 500 nm, increases steeply past 550 nm, reaches a sharp maximum peak at 620 nm with an absorbance value of 0.85, and falls sharply to 0.10 at 700 nm. No other curves, text, or annotations appear.](https://nerd-notes.com/wp-content/uploads/ubq-frq-generated/stem-fig-1-1790596930-3jn60s.jpg)

- **A.** The optimal wavelength is \(440\text{ nm}\), and the solution appears orange because light at \(440\text{ nm}\) is transmitted without being absorbed.
- **B.** The optimal wavelength is \(620\text{ nm}\), and the solution appears blue because it strongly absorbs light in the orange region (\(\approx 620\text{ nm}\)) and transmits the remaining visible wavelengths.
- **C.** The optimal wavelength is \(620\text{ nm}\), and the solution appears orange because the dye molecules absorb and re-emit light at \(620\text{ nm}\).
- **D.** The optimal wavelength is \(440\text{ nm}\), and the solution appears blue because it absorbs light most strongly in the blue region (\(\approx 440\text{ nm}\)).

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/123723/*