Measuring Light Flicker

Source: In its simplest definition, flicker is the constant fluctuation of light output from on to off. Because electricity is delivered through alternating current at a power line frequency of 50Hz in Singapore, the voltage delivered to a source bounces between on and off as it rides the sine wage between the positive and negative

LED Vs CFL: light spectrum comparison

Source of graph: Below diagram shows the spectrum a LED lamp (blue), a CFL (green) and an Incandescent (purple) superimposed the solar spectrum (yellow). Note that the energy used by each lamp is at least the area underneath its curve. You can see why LED lights are more efficient than incandescent lights and CFL lights.