Which one is having lesser ressistance. a 60w bulb or a 40w bulb?

Power dissipation = (voltage across the component) ² / (resistance of the component)

Since the resistance is in the denominator of the fraction in this formula for the

quantity of power dissipated, you can see that when the supply voltage is constant,

the smaller resistance dissipates more power.

So the 60w bulb has lower resistance than the 40w bulb.