A red postage stamp is viewed in yellow (monochromatic) light. It appears

Options

A. light grey
B. orange
C. black
D. deep yellow

Explanation

To solve the question regarding the appearance of a red postage stamp when viewed under yellow monochromatic light, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Color Perception**:
- Colors are perceived based on the wavelengths of light that are reflected off an object. A red postage stamp appears red because it reflects red wavelengths and absorbs other colors.

2. **Identifying the Light Source**:
- In this scenario, the light source is yellow monochromatic light. This means that the light consists only of yellow wavelengths.

3. **Analyzing the Interaction**:
- When the yellow light shines on the red stamp, we need to consider what happens to the light. The red stamp reflects red light and absorbs all other colors.

4. **Absorption of Yellow Light**:
- Since the stamp is red, it does not reflect yellow light. Instead, it absorbs the yellow light that hits it.

5. **Resulting Color Observation**:
- Because the red stamp absorbs the yellow light and does not reflect any light back to the observer, it will appear black.

6. **Conclusion**:
- Therefore, when viewed under yellow monochromatic light, the red postage stamp will appear black.

### Final Answer:
The red postage stamp appears **black** when viewed in yellow monochromatic light.

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