Sources of resources.
SECONDARY PHYSICS BK 3 (moran) pp 22-34
https://www.google.com/search?q=refraction+of+light&source
https://www.google.com/search?ei=Yh72XOqYCcL0aKGJlIgD&q=application+of+total+internal+reflection&oq
https://www.google.com/search?q=critical+angle&hl=en-KE&authuser
https://www.google.com/search?ei=0CD2XJSmLq3ClwTK54LoBA&q=total+internal+reflection+conditions&oq