Two electric bulbs have tungsten filament of same length. If one of them gives 60 watts and other 100 watts, then

$\mathrm{R}\propto \frac{1}{\mathrm{P}}$
Hence resistance of 60 watt bulb will be more than resistance of 100 watt bulb
Further R $=\mathrm{\rho }\left(\frac{1}{{\mathrm{\pi r}}^2}\right)\text{ or }\mathrm{R}\propto \frac{1}{{\mathrm{r}}^2}$
So, the radius of 100 watt bulb will be more than 60 watt bulb. Hence 100 watt bulb has thicker filament