Which color is produced by the emission of the highest energy photons?

Emission of the photons with the highest energy produces gamma rays, and you would not want to get any of those in your eye.  I don't know what color sensation they might produce, if any, but it could be the last color sensation you would ever experience with that eye.

WITHIN the range of wavelengths/frequencies perceptible to the human visual system, the highest-energy photons are the ones associated with the last color you can see on the VIOLET end of the rainbow.

what type of charge does it have? negative

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.