If loop of Henle is long in a nephron, the urine will be

If loop of Henle is long in a nephron, the urine will be more concentrated.

Countercurrent multiplication involves the long nephron loops of juxtamedullary nephrons. Juxtamedullary nephrons have long loops of Henle. Since the filtrate flows parallelly (countercurrent) descending and ascending limbs of the long nephron loop, an osmotic gradient is established in the renal medulla. The long nephron loop is said to function as a countercurrent multiplier. This osmotic gradient is used by the kidneys to excrete concentrated urine.