Given:

Area of square field = 0.5 hectare = 5000 m²

Let the side of square = x m

We know that,

Area of a square = side²

⇒ 5000 = x²

⇒ x = 50√2

Now,

Hypotenuse² = Base² + Perpendicular²

= (50√2)² + (50√2)²

= 5000 + 5000

= 10000 m²

Therefore,

Diagonal = √10000

= 100 m