The caste system in India divides its people in 4 main groups: Brahmins, priests and teachers; Kshatriyas, warriors and rulers; Vaishyas, farmers, merchants and traders; and the Shudras, labourers. This caste system isn't based on political views, but on the religious belief that each group originated from a different part of Brahma's body, the Hindu God of Creation.
India's caste system is very unfair and problematic. Three ways in which it has created social problems in the country are: 1) it prohibits people to change occupation and advance in life by making something else than what they were "born" to do; 2) it increases prejudism and discrimination towards certain groups as it doesn't let persons from different categories to mix in; and 3) it maintains a big social and economic gap between each group, which leads to violence and poverty.
Visible light is the small part within the electromagnetic spectrum that human eyes are sensitive to and can detect. Visible light waves consist of different wavelengths.
