Tangential velocity refers to the velocity at which a point on the blade of a Pelton wheel moves in a circular path. It is the velocity component that is tangent to the circle at that point. The tangential velocity of the blade is determined by various factors such as the speed of the wheel, angular velocity of the wheel, and the RPM of the wheel.

However, the correct answer to this question is option 'A' - the tangential velocity of the blade is proportional to the speed of the wheel.

Explanation:
The speed of the wheel refers to the linear velocity at the circumference of the wheel. It is the distance traveled by a point on the circumference in a given time.

When the wheel rotates, the points on the circumference move in circular paths. The tangential velocity is the component of velocity that is parallel to the tangent of the circular path at a given point.

The tangential velocity can be calculated using the formula:

Vt = rω

Where:
Vt = Tangential velocity
r = Radius of the wheel
ω = Angular velocity of the wheel

From this formula, it can be observed that the tangential velocity is directly proportional to the radius of the wheel and the angular velocity. However, the speed of the wheel is directly proportional to the product of the radius and the angular velocity.

If we consider two wheels with the same angular velocity, the wheel with a larger radius will have a higher speed. Similarly, if we consider two wheels with the same radius, the wheel with a higher angular velocity will have a higher speed.

Therefore, it can be concluded that the tangential velocity of the blade of a Pelton wheel is proportional to the speed of the wheel.