The correct answer is option 4: 80 cm and concave lens.
In optometry, myopia refers to nearsightedness, where distant objects appear blurry. The power of a lens is measured in diopters (D). A negative power indicates a concave lens, which is used to correct for myopia.
To determine the focal length of the lens, we use the formula:
Focal Length (f) = 1 / Power (P)
The power of a lens in diopters (P) is given as -1.25 D in this question.
Using the formula, we can calculate the focal length as:
f = 1 / (-1.25) = -0.8 m = -80 cm
Hence, the focal length of the lens is -80 cm or 80 cm (when we ignore the negative sign).
Since a negative focal length indicates a concave lens, the nature of the lens is concave.
Therefore, option 4, which states 80 cm and concave lens, is the correct answer.