How does the voltage affect the brightness of a bulb?

Year 6 dusted off their lab coats this week as they completed their first Science investigation of the year. We were looking at how the brightness of a bulb is affected by the amount of power (measured in volts) that the bulb receives. Before we began, like true scientists, we checked we had the correct equipment, wrote up our methods and made predictions. We used an iPad app called LUX to measure the intensity of the light bulb.