An energy-saver light-bulb of 11w gives the same illumination as a conventional 60w light-bulb. a typical light-bulb is used on average for five hours a day, how much energy is saved per year by one light-bulb? 2. if each household used eight such light-bulbs, and there are 20 mi- lion households in a country, how much energy would that country save annually?

882000 J

51508800000 Joules

Explanation:

First  we need to convert the units

11 W = 11 J/s

60 W = 60 J/s

5 hours = 5×60×60 = 18000 seconds

The amount of power saved

60-11 = 49 W = 49 J/s

The amount of energy saved in 5 hours in a day

49 J/s × 18000 s = 882000 J

Energy saved in one day is 882000 J

There are 20 million households with each of them having 8 light bulbs in the country

So, energy saved in one year would be

882000×8×20×10⁶×365 = 51508800000 Joules

Energy saved in one year is 51508800000 Joules

convex lenses are thicker at the middle. rays of light that pass through the lens are brought closer together (they converge). a convex lens is a converging lens. when parallel rays of light pass through a convex lens the refracted rays converge at one point called the principal focus.