Final answer:
A focal spot smaller than 0.3 requires a small intense laser, and the intensity in the focal spot increases with increasing NA, which can risk photodegrading the specimen. Focal length, such as one given at 8.00 cm, defines the distance from the lens to the spot.
Step-by-step explanation:
If the focal spot is less than 0.3, you use a small intense laser. In wave optics, due to diffraction, the focal point spreads to become a focal spot with the size of the spot decreasing with increasing numerical aperture (NA). Thus, the intensity in the focal spot increases with increasing NA. However, with a high NA, there's also a higher risk of photodegrading the specimen because of this intensity. Despite the reduction in size, the spot never becomes a true point.
When considering the focal length of a lens, which is the distance from the center of the lens to the spot, like being given as 8.00 cm, this value is crucial for understanding how the image will be projected. It's also important to note that the focal distances must be in centimeters, and a negative sign indicates an inverted final image.