in monochromatic red light a blue book will appear?
black. the blue book absorbs all the red, leaving nothing to be reflected to the eyes.
In the ideal circumstance, Bloodthunder is right. But of course, there are infinite shades of blue. Many blues contain a lot of red.
Technically, it would only appear black if the reflection coefficient at said wavelength is precisely zero.
The apparent spectrum (as visible to an observer) is the incident light times the reflection spectrum.
P.S. Sounds like a homework question.
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