Question

Why is chlorophyll green? a. It absorbs all wavelengths in the visible spectrum. b. It absorbs wavelengths only in the red portions of the spectrum \((680-700 \mathrm{nm})\) c. It absorbs wavelengths only in the blue part of the visible spectrum (450-480 nm). d. It absorbs wavelengths in only the blue and red parts of the visible spectrum.

Short answer

The short answer: Chlorophyll is green because it absorbs wavelengths primarily in both the blue and red parts of the visible spectrum, while reflecting green light.

Step-by-step solution

Understand Chlorophyll and its Function

Chlorophyll is a pigment found in plants, algae, and cyanobacteria, which plays a crucial role in the process of photosynthesis. It has the ability to absorb light energy from the sun and convert it into chemical energy through the process of photosynthesis. Its color is a result of the wavelengths it absorbs and reflects.

Analyze the Absorption Spectrum of Chlorophyll

In order to understand why chlorophyll appears green, we need to analyze its absorption spectrum. The absorption spectrum of a pigment is a graph showing the wavelengths of light absorbed by the pigment. Chlorophyll's absorption spectrum indicates that chlorophyll mainly absorbs blue and red light (short and long wavelengths) but reflects green light (medium wavelengths).

Evaluate the Given Options

Now, we will evaluate each of the given options to see which one matches chlorophyll's absorption properties: a. Chlorophyll does not absorb all wavelengths in the visible spectrum – it mainly absorbs blue and red light. b. Chlorophyll does absorb wavelengths in the red portions of the spectrum \((680-700\,\text{nm})\), but this is not the only reason why it is green. c. Chlorophyll does absorb wavelengths in the blue regions (450-480 nm), but this is also not the only reason why it is green. d. Chlorophyll absorbs wavelengths primarily in both the blue and red parts of the visible spectrum. It reflects the green light, which is the reason behind its green color.

Identify the Correct Answer

Based on the absorption spectrum of chlorophyll and evaluating each option, the correct answer is: \(d. \) It absorbs wavelengths in only the blue and red parts of the visible spectrum.

Key concepts

Photosynthesis

Photosynthesis is a fascinating and essential process that powers nearly all life on Earth. It is the method by which plants, algae, and some bacteria convert light energy from the sun into chemical energy in the form of glucose. During this process, these organisms take in carbon dioxide ( CO_2 ) and water ( H_2O ), and with the help of sunlight, they produce glucose (a type of sugar) and release oxygen ( O_2 ) as a byproduct.

Here's a simple overview of how it works:

• Light Absorption: Chlorophyll, the green pigment in plants, absorbs light primarily in the blue and red parts of the light spectrum.
• Conversion: The absorbed light energy is converted into chemical energy during the light-dependent reactions of photosynthesis.
• Synthesis: This chemical energy is then used in the Calvin cycle to synthesize glucose from CO_2 and H_2O .

Photosynthesis is not only crucial for plants, but it also provides the oxygen we breathe and is the foundation of the food chain.

Absorption Spectrum

The absorption spectrum of a substance like chlorophyll reveals the specific wavelengths of light that the substance can absorb. When light passes through or is reflected off an object, certain wavelengths are absorbed more than others, creating a pattern or graph that shows these variations.

For chlorophyll, the absorption spectrum is particularly interesting. It demonstrates high absorption at two regions:

• Blue Region: Around 450-480 nm
• Red Region: Around 680-700 nm

The absorption spectrum helps scientists understand which wavelengths of light are utilized most effectively by chlorophyll for photosynthesis.

This is why chlorophyll appears green; it absorbs the blue and red light and reflects the green wavelengths, which are then perceived by our eyes.

Pigment

A pigment is a substance that imparts color by absorbing certain wavelengths of light and reflecting others. Pigments are essential not just in art and dyes, but also in biological processes like photosynthesis. Chlorophyll is a prime example of a pigment found in nature.

Chlorophyll, the green pigment in plants, plays a key role in capturing light energy for photosynthesis. The reason it appears green is due to its specific absorption pattern, where it absorbs mainly blue and red light and reflects the green wavelengths.

Other pigments can be found in plants as well, such as carotenoids, which absorb light in different regions of the spectrum, contributing to photosynthesis and giving plants a variety of colors beyond just green.

Visible Spectrum

The visible spectrum is the portion of electromagnetic radiation that is visible to the human eye. It consists of light wavelengths ranging from about 400 nm to 700 nm, encompassing the colors we perceive in a rainbow.

The visible spectrum includes all the colors we know:

• Violet: About 400-450 nm
• Blue: About 450-495 nm
• Green: About 495-570 nm
• Yellow: About 570-590 nm
• Orange: About 590-620 nm
• Red: About 620-750 nm

Each color corresponds to a different wavelength range and can be absorbed, reflected, or transmitted by different materials.

Objects appear in certain colors based on the wavelengths they reflect. For chlorophyll, its green appearance in the visible spectrum results from reflecting light in the green wavelength, while absorbing others.