Cosmic rays are: d. high-energy particles.
Cosmic radiations are usually defined as a type of radiations that is comprised of high-energy photons and carry harmful ultraviolet radiation from the sun. These are emitted from the sun at a speed that is equivalent to the speed of the light.
When these radiations are incident on earth, it interacts with the upper atmosphere, resulting in the emission of charged particles such as pions, which undergoes decay and releases other smaller particles, commonly known as muons. These high-energy particles arriving from outer space are mainly (89%) protons – nuclei of hydrogen, the lightest and most common element in the universe – but they also include nuclei of helium (10%) and heavier nuclei (1%), all the way up to uranium. When they arrive at Earth, they collide with the nuclei of atoms in the upper atmosphere, creating more particles, mainly pions.
Thus, the correct answer is option (d).
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