Question

What is the third law of Kepler's Planetary Motion

Answer 1

 The total orbit times for planet 1 and planet 2 have a ratio a13/2 : a23/2.

Answer 2

$\huge\textbf{Kepler's Third Law :}$

According to it the square of time period of revolution of planet around sun is directly proportional to the cube length of semi major axis.

i.e. ${T}^{2}$ $\alpha$ ${R}^{3}$

Here T is time period of revolution and R is the distance of planet from the earth.

When we remove the sign of directly proportional then we have have to write some constant.

So, 

${T}^{2}$ = $k$ ${R}^{3}$

$\frac{{T}^{2}}{{R}^{3}}$ = $k$