Physics IA critical angle of glass
Aim
To determine the critical angle of glass using a glass block
Principle and Hypothesis
The Snell’s Law of Refraction says that –
At the boundary between any two given materials the ratio of the sine of the angle of incidence and the angle of refraction is constant for any particular wavelength.
The refractive index is determined by the formula –
R = Sin i Sin r
Where
i = angle of incidence of the ray of light r = angle of refraction of the ray of light
The refractive index of a medium gives the light bending ability of the material. When light passes from one medium to another it is bent, the extent to which it is bent depends on the value of the refractive index of the material. When light passes from one material into a material with greater refractive index (optically more dense) the light is bent towards the normal, when light passes from one medium to a medium with a lesser refractive index (less optically dense medium), the light is bent away from the normal.
Using a glass block it is possible to obtain the value of the critical angle of glass. By taking a particular angle of incidence it is possible to determine the angle of refraction, and this can be repeated for different values of i and r. Then if a graph is drawn between Sin r and Sin i, the gradient is 1/refractive index. Hence, knowing that Sin c = 1/refractive index. Thus the critical angle of glass is Sin-1 (1/refractive index).
It is important that the same block is used throughout the experiment. This is because even though glass might be considered to have a constant refractive index and hence constant critical angle, for experimental purposes it is quite possible that different glass blocks have different critical angles.
Even more importantly the source of light should be constant throughout the experiment, this is because the same material has differing refractive index and hence different critical angle for different wavelengths of life. Moreover,
To determine the critical angle of glass using a glass block
Principle and Hypothesis
The Snell’s Law of Refraction says that –
At the boundary between any two given materials the ratio of the sine of the angle of incidence and the angle of refraction is constant for any particular wavelength.
The refractive index is determined by the formula –
R = Sin i Sin r
Where
i = angle of incidence of the ray of light r = angle of refraction of the ray of light
The refractive index of a medium gives the light bending ability of the material. When light passes from one medium to another it is bent, the extent to which it is bent depends on the value of the refractive index of the material. When light passes from one material into a material with greater refractive index (optically more dense) the light is bent towards the normal, when light passes from one medium to a medium with a lesser refractive index (less optically dense medium), the light is bent away from the normal.
Using a glass block it is possible to obtain the value of the critical angle of glass. By taking a particular angle of incidence it is possible to determine the angle of refraction, and this can be repeated for different values of i and r. Then if a graph is drawn between Sin r and Sin i, the gradient is 1/refractive index. Hence, knowing that Sin c = 1/refractive index. Thus the critical angle of glass is Sin-1 (1/refractive index).
It is important that the same block is used throughout the experiment. This is because even though glass might be considered to have a constant refractive index and hence constant critical angle, for experimental purposes it is quite possible that different glass blocks have different critical angles.
Even more importantly the source of light should be constant throughout the experiment, this is because the same material has differing refractive index and hence different critical angle for different wavelengths of life. Moreover,