Listening Part 5: Fill in the blanks
PTE Listening Part 5- Sample 1: Fill in the Blanks
A clear sky during any time of the day is blue because molecules in the air scatter blue light more than any other colour. Sir Isaac Newton demonstrated with the help of a prism how a spectrum is formed. Each colour is visible differently because of different wavelengths. John Tyndall discovered that the shorter the wavelength of the colour, the more it spreads. As red has the largest wavelength, it scatters the least. This is the reason why the danger signals are red in colour, because as they have the longest wavelength, they are the most visible from far away. Though this phenomenon of scattering of light is most correctly called Tyndall Effect, but more commonly it is referred to as the Rayleigh scattering, after Lord Rayleigh who studied the phenomenon in more detail. Admittedly technical for many, Rayleigh concluded that the amount of light scattered is inversely proportional to the fourth power of wavelength for sufficiently small particles.