What does half an acre look like?
Keeping this in view, what is the size of a half acre lot?
An acre is 43560 square feet so half an acre is 43560/2 = 21780 square feet. If your 1/2 acre plot of land is a square with area 21780 square feet then each side is of length √21780 feet.
Similarly, you may ask, how big is an acre visually?
43,560 square feet
Each acre is 43560 square feet, so half of that is half an acre.