Which of the following has minimum stopping potential?

Options

A. Blue
B. Yellow
C. Violet
D. Red

Answer

To determine which of the given colors (blue, yellow, violet, and red) has the minimum stopping potential, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Stopping Potential**:
- Stopping potential is the potential difference needed to stop the photoelectric current produced by photoelectrons. It is directly related to the energy of the incident photons.

2. **Relate Energy to Wavelength**:
- The energy of a photon is given by the equation:
\[ E = \frac{hc}{\lambda} \]
where \( E \) is the energy, \( h \) is Planck's constant, \( c \) is the speed of light, and \( \lambda \) is the wavelength.
- From this equation, we can see that energy is inversely proportional to wavelength (\( \lambda \)). This means that as the wavelength increases, the energy decreases.

3. **Identify Wavelengths of Given Colors**:
- The wavelengths of the colors in the visible spectrum are approximately as follows:
- Violet: ~400 nm
- Blue: ~450 nm
- Yellow: ~570 nm
- Red: ~700 nm
- Among these, red has the longest wavelength.

4. **Determine Stopping Potential**:
- Since stopping potential is directly proportional to the energy of the photons, and energy is inversely proportional to wavelength, the color with the longest wavelength (red) will have the lowest energy and thus the minimum stopping potential.

5. **Conclusion**:
- Therefore, among the options provided, red has the minimum stopping potential.

### Final Answer:
The color with the minimum stopping potential is **red**.

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