Q:

Optimal monitor resolution

Currently, there are a lot of monitors capable of displaying 4K resolutions, for example the one used in this Alienware laptop. This laptop has 15 inch display with 4K resolution. I have a few questions regarding this high resolution, yet "small" size display:

What are the optimal resolution for 15 inch display, i.e. is it really needed to have 4K resolution so that human eye cannot distinguish adjacent pixels? and how about 14 inch display, 17 inch, etc, what is the formula to calculate what's the best resolution?
Does the number of pixels greatly affect the power consumption, or is it the size of the display that determine how much the power consumption is (in terms of the display, not the graphic card)?

A:

For the Question 1:
For the recommended resolution for your monitor can be viewed in your windows.
Click here to learn as to how find the the recommended resolution for your monitors in windows. 
4K resolution are used usually in Ultra HD monitors(Larger display).
The more the no. of pixels  the high will be the picture quality. 
Consider below two cases. 
Case 1:
If you take two displays of same size, one with higher no.of pixels than the other, then the display with more pixels will have better picture quality.
Case 2:
Take two monitors of different size but both have same no. of pixels(relatively more) you can see the adjacent pixels in larger display than the smaller one. 
Hence the adjacent pixels not to be seen by human eye depends not only on no. of pixels also on the relative size of the display.
To know more please refer at 4k resolution, Pixel, Aspect Ratio, Aspect ratio Calculator
For Question 2:
Refer HERE

