**1 ^{st} law or the law of isochronism: **

The time period (T) is constant when effective length (L) and gravity (g) are constants. This means that a pendulum will take same time in completing each oscillation, whatever is the amplitude, provided the latter does not exceed 4^{o}. So the time period of oscillation of a simple pendulum is independent of the amplitude of vibration, provided its amplitude does not exceed 4^{o}.

**2 ^{nd} law or the law of length:**

When acceleration due to gravity (g) is constant, the time period (T) of oscillation of a simple pendulum is directly proportional to the square root of its effective length (L).

So, T ∞ √L, when g is constant.

**3 ^{rd} law or the law of acceleration:**

When effective length (L) is constant, the time period (T) of oscillation of a simple pendulum is inversely proportional to the square root of the acceleration due to gravity (g) at a place of observation.

So, T ∞ √1/g, when L is constant.

**4 ^{th} law or the law of mass:**

The time period of oscillation of a pendulum at a place independent of mass and material of the bob provided the effective length of the pendulum is constant.