Here is a good reference to further explain the specular reflection and refraction: http://www.pbr-book.org/3ed-2018/Reflection_Models/Specular_Reflection_and_Transmission.html
Here is a good reference to further explain the specular reflection and refraction: http://www.pbr-book.org/3ed-2018/Reflection_Models/Specular_Reflection_and_Transmission.html