A student investigated how length affects resistance of a wire. Figure 1 shows the circuit the student used.
The student took measurements using the meters X and Y.
Name meters X and Y. The table shows the results. For which length of wire are the readings of resistance most precise

The focal length of a relaxed human eye is approximately 1.7 cm. when we focus our eyes on a close up object, we can change the refractive power of the eye by about 16 diopters. (a) does the refractive power of our eyes increase or decrease by 16 diopters when we focus closely? explain. (b) calculate the focal length of the eye when we focus closely.