Name one advantage and one disadvantage of the prepaid electricity system.​

The system prevents a consumer from accruing debt via electricity use, as it only allows the customer to use electricity which has been paid for upfront.

this gives the advantage of not allowing the consumer to rack up debt

the disadvantage for the consumer comes when they cannot afford to prepay in a time of financial difficulty - as the system now renders them as having no electricity as well as no money

explanation:

v=uf/(u-f)

= 5.-10/(5+10) convex lens has negative focal length

scattering of light by tiny particles in air to produce the colors we see on sky, is dependent on the following factors:

(i) wavelength of light

(ii) size of the scattering particle  

(iii) distance traveled by light through the atmosphere.

according to rayleigh's law of scattering, the amount of scattering is inversely proportional to the fourth power of its wavelength. shorter the wavelength, greater is its scattering. hence violet/blue light is scattered more than red.

sun's light is a composite light ( visible light) with wavelengths in the range 400 nm (violet) to 700 nm (red). as sunlight passes through our atmosphere, the molecules of air scatter light according to their wavelengths. during sunrise and sunset, the sun's position is below the horizon. hence light from the sun travels a greater distance in the atmosphere when compared to its position a noon.

as sunlight enters the earth's atmosphere, blue light is scattered away and at the end of its journey in the sky, only red and orange wavelengths remain in the beam.

hence at sunrise and sunset, the sky appears reddish orange.