The device is 50% efficient. Which equation is correct? A input energy = useful output energy ÷ 2 B useful output energy =wasted output energy ÷ 2 C wasted output energy = useful output energy D wasted output energy = useful output energy ÷ 2

C - wasted output energy = useful output energy

Explanation:

Useful output + wasted output ALWAYS equals input energy. If the device is 50% efficient, that means that 50% of the input energy is converted into useful output energy, and 50% is converted to wasted output energy. The wasted output energy is equal to the useful output energy.

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.