Answer:
7.402%
Step-by-step explanation:
Given that the total electrical energy used by the bulb in every second is 66.2 J.
The useful energy converted to light energy is 4.9 J.
As efficiancy (in %) = (Useful energy)/(Total energy) x 100
So, the efficiency of the bulb = (4.9/66.2)x100=7.402%
Hence, the efficiency of the bulb is 7.402%.