A pure substance is a substance that is made with only one type of molecule
The angle of refraction is 15.6 deg.
When a ray of light passes from medium 1 to medium 2, the refractive index of medium 2 with respect to 1 is the ratio of the absolute refractive index of medium 2 and medium 1

When light passes from air into diamond, with the given values of refractive indices,

According to Snell's law,

The angle of refraction is 15.6 deg
Explanation:
C. neutron.
it does not contain ionizing characteristics.
hope it helps. :)
Internal energy.
Explanation:
In any substance/object, the particles inside it (atoms/molecules) constantly move in random directions and with random speeds (this motion is called Brownian motion). As a result, the particles have some kinetic energy (which is proportional to the temperature of the substance). Moreover, the particles interact with each other due to the presence of electrostatic intermolecular forces, and as a result, the particles also have some potential energy.
The sum of the kinetic energies and potential energies of the particles in a substance is called internal energy.
Answer: repeatable
Explanation: Accurate repeatable is needed in a valid experiment. I think