Red drop occurs in wavelength of

Options

A. 495 nm
B. 680 nm
C. 560 nm
D. 586 nm

Answer

**Step-by-Step Solution:**

1. **Understanding Red Drop**: The term "red drop" refers to a phenomenon observed in photosynthesis where there is a sharp decrease in quantum yield at certain wavelengths of light. Quantum yield is the number of specific events (like the release of oxygen molecules) that occur per photon absorbed by the photosynthetic system.

2. **Defining Quantum Yield**: Quantum yield can be defined as the number of oxygen molecules released per quantum of light absorbed. It is typically expressed as a ratio, indicating how many molecules are produced for every photon absorbed.

3. **Identifying the Wavelength**: The question specifically asks about the wavelength at which the red drop occurs. Research indicates that the red drop phenomenon is observed when the wavelength of light exceeds 680 nanometers.

4. **Analyzing the Options**: The options provided include various wavelengths:
- 490 nanometers (incorrect)
- 680 nanometers (correct)
- Other wavelengths (not specified but assumed incorrect)

5. **Conclusion**: Based on the understanding of the red drop phenomenon and the analysis of the options, the correct answer is that the red drop occurs at wavelengths greater than 680 nanometers.

**Final Answer**: The red drop occurs at wavelengths greater than 680 nanometers.

---