Why does a diamond shine more than a glass piece cut to the same shape?

Hint: Shining of the diamond or the glass piece cut to the same shape will be dependent on the extent of the phenomenon of the total internal reflection or the phenomenon of the reflection. Total internal reflection occurring through a body will be dependent on the refractive index and the critical angle for the particular material.

Complete answer:
On comparing the refractive index of the diamond and glass we find that the refractive index of the diamond is more than that of the glass. This will result in a more critical angle of the glass than that of the diamond and we all know that the material of less critical angle will give more total internal reflection. So, the diamond gives more total internal reflection than that of the glass. so, in the diamond total internal reflection takes place while in the glass piece cut to the same shape are less prone to have total internal reflection.



Thus, due to this reason of more total internal reflection of the diamond than the glass the diamond shines more than a glass piece cut to the same shape.

Note:
Total internal reflection (TIR): - When a ray of light is going from one medium to another then it is subjected to the two different media having two different refractive indexes and this makes the ray of light to refract. But when the refractive index of the medium in which the ray is going is very less then the ray of light encounters the incident angle less than a specific critical angle for the particular medium. So, when the incident angle of the incoming ray of light exceeds the critical angle of the medium then the ray of light will get reflected back in the same medium, and this phenomenon is known as total internal reflection.