KEPLER'S LAWS OF PLANETARY MOTION
Kepler I law:
Every planet revolves around the sun in an elliptical orbit with the sun is at one of its foci. This law is also known as the law of Orbits.
Kepler II law:
The radius vector drawn from the sun to the planet gives equal areas in equal interval of time. That means the rate of change of the area of the planet / areal velocity is constant. This law is also known as the law of areas.
Kepler III law:
The time period (T) of the planet revolving around the sun is directly proportional to the cube of the semi-major axis (a) of the orbit. This law is also known as the law of periods.
i.e T2 α a3