This question asks us to identify the statement that is NOT a law or characteristic property of static friction. Let's analyze each option:

Understanding Static Friction Properties

• Option 1: Limiting friction × Normal reaction = Constant

  This statement is presented as Limiting friction × Normal reaction = Constant. The actual relationship between limiting friction ($F_l$) and the normal reaction force ($N$) is given by the formula $F_l = \mu_s N$, where $\mu_s$ is the coefficient of static friction. The coefficient $\mu_s$ is a constant for a given pair of surfaces in contact. The statement provided incorrectly suggests multiplication of limiting friction and normal reaction equals a constant, which is not a correct physical law.

• Option 2: The force of friction is independent of the area of contact between the two surfaces.

  This is a well-established principle for friction, including static friction, under typical conditions. It means that whether you slide a book flat on a table or on its spine, the friction force remains the same, assuming the normal force is constant.

• Option 3: The magnitude of force of friction is exactly equal to the force, which tends to move the body.

  Static friction acts as a reaction force. It opposes the applied force that tries to cause motion. As long as the body remains stationary, the static friction force precisely matches the applied force, up to its maximum possible value (the limiting friction). So, if you push a heavy box lightly, static friction equals your push. If you push harder, static friction increases to match it, until you exceed the limiting friction.

• Option 4: The force of friction depends upon the roughness of the surfaces.

  The 'roughness' or the nature of the surfaces in contact is a key factor determining the coefficient of friction ($\mu_s$). Rougher surfaces generally have a higher coefficient of static friction, leading to a larger friction force for the same normal force.

Identifying the Incorrect Law

Comparing the options with the known principles of static friction:

• Options 2, 3, and 4 describe valid characteristics or laws related to static friction.
• Option 1 presents a mathematically and conceptually incorrect relationship. The correct relationship involves the coefficient of static friction $\mu_s$, stating that the limiting friction is directly proportional to the normal reaction ($F_l = \mu_s N$), not that their product is constant.

Therefore, the statement "Limiting friction × Normal reaction = Constant" is NOT a law of static friction.