Let us suppose that V is the voltage on each bulb and R1 and R2 be the resistance of the 60 watts bulb and 100 watts bulb respectively. Then,

\(R_1=\frac{V^2}{P_1}\), and

\(R_2=\frac{V^2}{P_2}\)

Where P1 = 60 W and P2 = 100 W

\(\therefore\frac{R_1}{R_2}=\frac{P_2}{P_1}\) i.e., \(R\propto\frac1P\)

From this relation, we conculde that the resistance of the 60 W bulbs is more than 100 W bulb. Since the brightness of the bulb is directly proportional to the heat developed, therefore, 60 W bulb glows more brightly thgan 100 W bulb.