1. Pigments:
* Chlorophyll: The green pigment in plants that absorbs red and blue light, using the energy to drive photosynthesis.
* Carotenoids: Found in plants and animals, these pigments absorb blue and green light, giving fruits and vegetables their orange, yellow, and red colors.
* Hemoglobin: The red pigment in blood that absorbs oxygen and transports it throughout the body.
* Melanin: The pigment responsible for skin, hair, and eye color, absorbing UV radiation and protecting us from its harmful effects.
2. Other Organic Molecules:
* DNA and RNA: These nucleic acids absorb strongly in the ultraviolet (UV) range, making UV spectroscopy a powerful tool to study them.
* Proteins: The structure and composition of proteins influence their light absorption. For example, the aromatic amino acids tryptophan, tyrosine, and phenylalanine have characteristic UV absorption.
* Organic dyes: These molecules are designed to absorb specific wavelengths, giving them vibrant colors and making them useful in textiles, food coloring, and other applications.
3. Inorganic Compounds:
* Transition metal ions: Many metal ions, especially those in the transition metal series, absorb specific wavelengths of visible light due to d-orbital transitions. This is why solutions of transition metal ions are often colored.
* Semiconductors: Materials like silicon and germanium absorb specific wavelengths of light, leading to their use in solar cells and other optoelectronic devices.
4. Spectroscopy:
* UV-Vis Spectroscopy: Used to identify and quantify molecules based on their unique absorption patterns in the ultraviolet and visible regions of the electromagnetic spectrum.
* Infrared (IR) Spectroscopy: Used to identify and analyze functional groups (like C-H, C=O, and O-H bonds) in molecules based on their absorption of infrared radiation.
Important Considerations:
* The Beer-Lambert Law: This law describes the relationship between the absorbance of a solution and the concentration of the absorbing species.
* Chromophores: These are specific parts of a molecule responsible for absorbing light.
* Auxochromes: These are groups that can modify the absorption spectrum of a chromophore by altering its electron distribution.
If you have a specific molecule in mind, I'd be happy to help you understand its light absorption properties in more detail.
