The graph shows absorption spectra of three food dyes: Blue No. 1, Red No. 2 and Yellow No. 4. What is the λmax for Blue No. 1?

Question

BlackTom AI · Accepted Answer

The question presents a reading of a graph showing absorption spectra for three food dyes and asks for the λmax of Blue No. 1.
Option a: 500 nm. This wavelength lies in the blue-green region. If Blue No. 1 had a maximum absorbance at 500 nm, it would imply strong absorption in the blue-green area and a complementary color of yellow-orange would be transmitted. However, the typical λmax for Blue No. 1 is not at 500 nm, so this is unlikely.
Option b: 620 nm. This wavelength is in the orange-red region. A dye that absorbs around 620 nm would appear blue to the eye because it absorbs red-orange light and transmits blue hues. Brillant Blue FCF (Blue No. 1) commonly exhibits a λmax near 620–630 nm in aqueous solutions, which aligns with known spectral data for this dye. Thus this option corresponds to the expected λmax for Blue No. 1.
Option c: 710 nm. This is in the red-infrared part of the spectrum. Absorption at such a long wavelength would indicate the dye absorbs far into the red, which is not characteristic of Blue No. 1; its absorption maxima are typically at shorter wavelengths than 710 nm. Therefore this choice is unlikely.
Option d: 530 nm. This sits in the green-yellow region. If Blue No. 1 absorbed at 530 nm, the dye would appear strongly orange to red with transmission in the blue region, which contradicts its established blue appearance and known λmax ranges. Hence this option does not match the expected maximum.
In summary, analyzing the color-absorption relationship and typical spectral data for Blue No. 1, the 620 nm maximum absorption (Option b) best explains the observed color and the graph’s peak for this dye, while the other wavelengths are inconsistent with the dye’s absorption profile.

The graph shows absorption spectra of three food dyes: Blue No. 1, Red No. 2 and Yellow No. 4. What is the λmax for Blue No. 1?单项选择题

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