How do you know about the holiday lights? Do you know?
The internal structure of the festive lanterns is different from the general lights. In addition to the filament, each lamp has a resistor connected in parallel between the two lamp pins. The resistance of this lamp is much larger than the resistance of the filament. Therefore, most of the current flowing through the small lamp is through the filament, and only a small amount of current passes through the resistor, so the small bulb normally emits light. When the filament is burned, the current passes through the resistor, and the voltage across the resistor is greatly increased, so that the voltage on the other lamps is reduced, so the other lamps become darker than the original.