What happens when one light bulb out of three goes out in a parallel circuit?

When three light bulbs are in parallel the voltage V on each is the same. Each bulb draws a certain amount of current, i1, i2, & i3. If all three are working they draw a total current I = i1 + 12 + 13 from your power source. And the energy they use is ,I x V. When one bulb goes out then the only thing affected is i3 = 0. The voltage is the same but the total current from your power source is less and therefore the total energy used is less. So nothing happens to the other two bulbs (that's one reason why all household outlets are in parallel) and you just use less energy.