Summer soltice is here! summer begins in the northern hemisphere and winter begins in the southern hemisphere. during summer soltice the northern hemisphere has more hours of daylight, that means today is the longest day and also the shortest night of the year. seasons occur due to the inclination of earth axis with respect to the ecliptic plane, which is the plane of its orbit around the sun.
image by jorge s. diaz. #summer#summersoltice2018#seasons#astronomy#physics
Rainbows exist because the refractive index of most optical media such as water depends on the wavelength and therefore the colour of the incident light. white light falling onto a water surface at an angle gets spread out and separated into its spectral colours because the different colours get refracted more or less strongly. in a water droplet, the light first gets refracted, then reflected (total reflection) at the backside of the droplet, then refracted a second time as it leaves the droplet at the front again. the two refractions separate the different spectral components of the white sunlight enough for our eyes to pick up on the colour differences and the reflection inside the droplet is the reason why the sun has to be behind us for us to be able to marvel at the beauty of such a rainbow.