Final answer:
Quantum noise on a digital image appears as graininess.
Step-by-step explanation:
Quantum noise can appear on a digital image as graininess. This is because quantum noise is caused by the random variation in the number of photons that hit the image sensor. When there are fewer photons, the image appears grainy and noisy.
For example, if you take a photo in low light conditions, the image may show more graininess due to the quantum noise. On the other hand, in well-lit conditions with more photons hitting the image sensor, the quantum noise is reduced, resulting in a smoother and less grainy image.