A wire hangs from a dark high tower so that its upper end is not visible.how can we determine the length of the wire?

One way to determine the length of the wire hanging from the tower is to measure the distance from the ground up to where the wire disappears from view. This measurement, along with the height of the tower, can be used to calculate the length of the wire using trigonometry. Alternatively, you could use a tool such as a rangefinder or laser distance measurer to directly measure the length of the wire.