What is the length of foot of perpendicular drawn from the point P (3, 4, 5) on y-axis

As y-axis lies on xy plane and yz.

So, its distance from xy and yz plane is 0.

∴ By basic definition of 3-D coordinate we can say that x-coordinate and z–coordinate are 0.

As, perpendicular is drawn from point P to y-axis, so distance of point of intersection of this line from xz plane remains the same.

∴ y-coordinate of the new point say Q = 4

Or we can say that corresponding point on y-axis is (0, 4, 0)

∴ Length of perpendicular = distance between P and Q

From distance formula-

PQ =

∴ Length of foot of perpendicular drawn from the point P (3, 4, 5) on y-axis is √34 units.

Hence, option(B) is the only correct choice.