Final answer:
The range of vision for a person whose vision is between 15 and 100 cm when they wear close-fitting spectacles of power -0.8 diopter cannot be accurately determined without additional information. Generally, the -0.8 diopter lens will help correct nearsightedness, allowing the person to see objects farther away more clearly.
Step-by-step explanation:
When a person with a vision range of 15 cm to 100 cm wears close-fitting spectacles of power -0.8 diopter, we must calculate the new range of vision. The power of a lens in diopters (D) is the inverse of its focal length in meters (1/D = f). For a lens with power -0.8 D, the focal length is -1.25 m (since 1/-0.8 = -1.25). This negative sign indicates that the lens is diverging, which is used to correct nearsightedness.
Nearsightedness, also known as myopia, is corrected by diverging lenses, which effectively push the far point of vision farther away and bring the near point closer to the eye. By using the lens formula 1/f = 1/do + 1/di and considering the lens-maker's formula, we can calculate the new near and far points of the lens-wearer's vision.
However, this question does not provide sufficient information to use these formulas directly nor does it reference a specific vision range for the glasses, typically the problem would be approached by combining the diopters of the glasses with the diopters of the nearsightedness to determine the corrected near and far point. Unfortunately, without the individual's original diopters for nearsightedness before wearing glasses, an accurate range cannot be determined with the information provided.
Therefore, without additional information or assumptions, we cannot confidently determine the new range of vision and can only articulate that in general, a -0.8 diopter lens will improve the person's ability to see farther away.