Question

photosynthesis begins with sunlight. if youve taken physics or have had a chance to study light in other contexts, you might remember that light has characteristics associated with both particles and waves. discrete particles of light are called photons. the pigments associated with each photosystem absorb a certain number of photons.
its also important to recognize that the light that strikes a leaf contains many different wavelengths. the set of wavelengths that are visible to humans is called the visible spectrum, and ranges from shorter wavelengths in the purple and blue part to longer wavelengths in the red part. shorter wavelengths contain more energy than longer wavelengths.
ultraviolet (uv) light is used in tanning salons and infrared (ir) light is used in heating lamps. both uv and ir light are in sunlight. uv light has shorter wavelengths than purple light and ir light has longer wavelengths than red light.
given this information, why is long - term exposure of skin to uv light more dangerous than long - term exposure of skin to ir light?
○ uv light contains much more energy than ir light — enough to damage proteins and nucleic acids.
○ uv exposure stimulates skin cells to synthesize the brown pigment melanin, which deepens skin color.
○ ir heaters are considered efficient because they only warm objects that absorb the energy, not the air.
however, plants use only a small fraction of the light energy that strikes them because the pigments that drive

Explanation:

The text mentions that shorter wavelengths contain more energy than longer wavelengths. UV light has shorter wavelengths than IR light. So, UV light has more energy. High - energy UV light can damage biological molecules like proteins and nucleic acids in the skin, while IR light (with lower energy as it has longer wavelengths) is less likely to cause such damage.

Answer:

UV light contains much more energy than IR light — enough to damage proteins and nucleic acids.