CBSE Class 10 Answered

Imagine nw a ray of light travelling from a denser medium to a rarer medium...for example air and water..where water being denser medium and water being rarer.. when this ray strikes the interface...its certain that the ray wud undergo refraction. The particular value of angle of incidence tht the incident ray makes with the normal such tht the angle of refractions bcomes 90 degree..tht is the refracted ray travels parallel to the interface. this particular value of angle of incidence is called critical angle..n if the angle of incidence still increases..then the ray wud be reflected back to the denser med.