Q.Name the two classes of accessory (secondary) pigments typically found alongside chlorophyll a in a green leaf.

Carotenoids -- carotene (orange, $C_{40}H_{56}$) and xanthophyll (yellow, $C_{40}H_{56}O_2$) -- are accessory pigments that broaden the range of usable light and protect chlorophyll from photo-oxidative damage under excess light. The absorption spectrum of a pigment (measured on an isolated extract, showing chlorophyll's two peaks in blue-violet and red, with a trough in green -- why leaves look green) is distinguished from the action spectrum (the actual photosynthetic rate of a living leaf at each wavelength, as Engelmann effectively measured via bacterial clustering). The close over …