Analyse why red sunsets can sometimes be more impressive when there is more dust or pollution in the air than usual.


Blue skies and red sunsets are not caused by refraction, but by another phenomenon known as scattering. Scattering is molecules of gas and dust particles in the atmosphere which alters the direction of light rays. Blue rays tend to scatter more than other colours of the spectrum. Blue light against the dark background of space causes the sky to appear blue. At sunrise and sunset, when sunlight travels further through the atmosphere, almost all of the blue rays are scattered and the light that reaches us is mainly red or orange.

Describe what happens inside water droplets to cause a rainbow and explain how you can tell whether a rainbow is a primary or secondary.


Small droplets of water behave like tiny prisms in the sky. Sometimes the colours will reach our eyes after refracting and undergoing total internal reflection. A primary rainbow is a band in the sky with red at the top and blue at the bottom. Secondary colours include of cyan, magenta and yellow.

Reference;
Taken from Science Focus 3 text book pages 110-111