Both the lens and the cornea of the eye have a primary function of
a. detecting colors
o b. bending light
c. letting in appropriate amounts of light

B. bending light

Explanation:

The phenomenom of vision in human eye is thanks to refraction (when light changes its direction as it passes through one medium to another), and this is what the cornea and the lens do.

When the ray of light encounters the eye, the first thing it finds is the cornea, which bends this ray and begins to form an image, then light passes through the pupil, which is in charge of regulating the amount of light that enters in the eye.  

After light travels through pupil it passes through the lens, where the rays of light change the direction again in order to focus the formed image on the retina.

At this point it is important to note the formed image is downward, then the retina transforms light into electrical impulses that are sent to the brain through the optic nerve and finally the brain interprets these messages, and forms a right upward image.

In the image attached these parts can be seen.

d) the number of neutrons plus the number of protons

the box does not move because you need to use a force greater than 300 n. you are only using 50 n. it needs to at least be 301 n for the box to move because then it is an unbalanced force and it will move the way that the greater force is pushing it. if you use only 300 n it will be a balanced force and will not move because the force you are exerting on the   box is the same as its force.

hope this !

im sorry if i went too in depth, i am going to include a link to a video on khan academy that will explain this.   hope that you like the video and that it explains more in detail to you.

that is the link.