In a hydrogen atom the radius of n^th Bohr orbit is ‘r_n’. The graph between log (r_n/r₁) taken on y-axis and log(n) on x-axis will be

${\mathrm{r}}_{\mathrm{n}}={\mathrm{r}}_1{\mathrm{n}}^2\Rightarrow \frac{{\mathrm{r}}_{\mathrm{n}}}{{\mathrm{r}}_1}={\mathrm{n}}^2$

$\Rightarrow \log \left(\frac{{\mathrm{r}}_{\mathrm{n}}}{{\mathrm{r}}_1}\right)=2\log \left(\mathrm{n}\right)$

So the graph between log (r_n/r₁) taken on y-axis and log(n) on x-axis will be a straight line passing through the origin.