[jambutty]

Much obliged for your brief science lesson Cyfr.

Visible light is indeed made up of various colours of light, which combined produce what we call white light. As you point out the full light spectrum can be seen by shining a beam of light through a prism or a raindrop or two to produce a rainbow.

I don’t know why I didn’t think of this earlier because I have the equipment and the ability to measure the current drawn by a normal 60 watts light bulb and the current drawn by a 60 watts low energy bulb. This would truly determine which was more energy efficient.

A 60 watts normal bulb draws 200mA at 230 volts.
A 60 watts energy efficient bulb draws 20mA at 230 volts. That is ten times less and is thus much more energy efficient because the energy being used is used to produce light and very little heat.

As entwisi points out the normal bulb produces an awful lot of heat as anyone who has tried to change a bulb that has just blown after being on for a few minutes will know to their cost. I have no idea what the temperature of the glass is but it is enough to inflict quite severe burns.

So the answer to the eternal question of “How many electricians does it take to change a light bulb?” the answer is three. One to grab the hot bulb and fall to the ground with third degree burns to his hand. One to administer first aid and send for the ambulance. One to get asbestos gloves and change the bulb.

The light that either bulb produces is in the visible spectrum and general purpose solar panels are activated by light in the visible spectrum be it in the red range or the blue or anything in between. So my calculator did indicate that a 60 watts energy efficient bulb does not give off quite so much light as a normal 60 watts bulb. The difference to the naked eye is barely noticeable, if at all, but instruments like a solar panel can ‘see’ the difference. My calculator will work in candlelight if I put it very close to the flame.

To get back to the topic, adding extra tax to light bulbs is just another scheme to extort more money out of the long suffering public and to try to force people into buying the energy efficient versions to replace the normal type.

If they really want people to change to the new type then the way to do it would be to have a scheme where we could return a normal bulb and get a new type for the price of the normal one or no more than half the cost of the new type. Obviously the sale of normal bulbs would have to be stopped.