Snell's Law | Physics for GCSE/IGCSE - Year 11 PDF Download

Refractive Index

• The refractive index is a number associated with the speed of light in a material, always slower than in a vacuum.

• The refractive index is always greater than 1 and varies for different materials.
  • Objects with higher optical density, like diamond (refractive index ~2.4), have higher refractive indices.
  • Objects with lower optical density, like glass (refractive index ~1.5), have lower refractive indices.
• Refractive index is a ratio and does not have any units associated with it.

Snell's Law

• When light transitions into a denser medium such as glass, it decelerates and bends towards the normal line.
  • The extent of light bending is contingent upon the density of the material.

• Light bending towards the normal: When light travels from a less dense medium (e.g., air) to a more dense medium (e.g., glass), the angle of refraction is less than the angle of incidence.
• Light bending away from the normal: When light travels from a more dense medium (e.g., glass) to a less dense medium (e.g., air), the angle of refraction is greater than the angle of incidence.
• Snell's Law mathematically describes the relationship between the angles of incidence and refraction.
  
• Where:
  • The refractive index (n) of the material affects how much light bends.
  • The angle of incidence (i) is the angle at which light enters the medium.
  • The angle of refraction (r) is the angle at which light changes direction upon entering the new medium.
• 'Sin' in Snell's Law refers to the trigonometric function 'sine,' typically found on scientific calculators.
• This equation can be rearranged with the help of the formula triangle: