which of the following is responsible for earth’s magnetic field?

a

molten metals in earth’s interior

b

earth’s oceans

c

the gravitational pull of the sun and the moon

d

earth’s orbit

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.