Need help please this is physics work

Are aliens real? justify you’re answer.

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.

When you push downward on a book at rest on a table, you feel an upward force. does this force depend on friction? defend your answer.