MCQ Detailed View

The color of a leaf depends on the light it reflects and absorbs. Green leaves appear green under white light because they absorb red and blue wavelengths of light for photosynthesis and reflect green light. This reflection of green light is what our eyes perceive as the color green.

When green leaves are placed under red light, the situation changes. Chlorophyll in the leaves absorbs red light for photosynthesis. Since there is no green light in the red light source, the leaf cannot reflect green light. As a result, the leaf absorbs most of the red light and very little is reflected to the observer’s eyes. Without reflected light, the leaf appears black.

This phenomenon demonstrates the principle of selective absorption and reflection of light by pigments. Chlorophyll a and b are the main pigments responsible for photosynthesis, and they have specific absorption peaks in the red and blue regions of the spectrum. Green light is minimally absorbed and mostly reflected under normal white light, giving leaves their green appearance.

Other options, such as green, red, or blue, are incorrect because the observed color depends on the wavelength of light that is reflected. Under red light, no significant green or blue wavelengths are present to reflect, and red light is mostly absorbed.

Understanding this concept is important in plant biology and photosynthesis studies. It illustrates how light quality affects the appearance and functioning of leaves. This knowledge is also applied in controlled plant growth environments, such as greenhouses using artificial light sources for optimal growth.