The two lenses would bee a double convex (in the eye) and the contact would be a convex, right?Simon Bridge said:The tear+contact must make a compound lens with the power needed to correct eyesight with the stated near-point.
How do the powers of lenses combine?
The formula for calculating the power of a lens is P = 1/f, where P is the power in diopters and f is the focal length in meters.
A positive power lens is a convex lens that converges light rays, while a negative power lens is a concave lens that diverges light rays. Positive power lenses are used to correct farsightedness, while negative power lenses are used to correct nearsightedness.
To calculate the power of a compound lens system, you can simply add the individual powers of each lens in the system. For example, if two lenses with powers of +4 diopters and -2 diopters are placed together, the resulting power of the system would be +2 diopters.
The unit of measurement for lens power is diopters (D). This unit is used to measure the refractive power of a lens, which is the ability of the lens to bend light.
The higher the power of a lens, the greater its ability to bend light. A lens with a higher power will have a shorter focal length, meaning it can bring light rays to a focus at a closer distance. A lens with a lower power will have a longer focal length, meaning it can bring light rays to a focus at a farther distance.