======Investigating Refraction and Snell's Law======


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**Alternative titles:** Refractive Index of Glass
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====Summary====                   
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====Procedure====  
  -Place a glass block on a sheet of plain paper and carefully draw around it.  
  -Draw a normal line (perpendicular) at one side of the block where the beam will enter.  
  -Use a protractor to mark out incident rays at different angles (e.g., 10°, 20°, 30°, … up to 80°).  
  -Shine a narrow light beam from a ray box along the first marked angle so it enters the block.  
  -Mark the entry point, exit point, and the path of the outgoing beam on the paper.  
  -Remove the block and join the marks to show the path of the light ray through the block.  
  -Measure the angle of incidence (i) and angle of refraction (r) with a protractor.  
  -Repeat for all chosen incident angles.  
  -Plot a graph of sin(i) against sin(r). The slope of the line gives the refractive index of the glass.



====Links==== 
PRACTICAL: How to conduct experiment on light refraction with a block and a ray box - Physics Rox: 
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Investigating refraction - Dr. Steve Griffiths: 
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📄 Investigating Snell's law - Katie M: [[https://www.savemyexams.com/igcse/physics/edexcel/19/revision-notes/3-waves/3-2-reflection-and-refraction/3-2-5-core-practical-investigating-snells-law/]]\\

====Variations====
  *Use a semicircular glass block instead of a rectangular one.  
  *Try different materials (perspex, plastic) to compare refractive indices.  
  *Use colored filters to test if wavelength affects refraction.



====Safety Precautions====
  *Ray box bulbs can become hot—avoid touching directly and allow cooling before handling.  
  *Do not look directly into the light beam.  
  *Ensure the experiment is done in a dimmed room but keep floors clear to avoid trip hazards.  
  *Keep liquids away from electrical equipment.




====Questions to Consider====
  *What happens to light when it passes from air into glass? (It slows down and bends toward the normal.)  
  *Why is a graph of sin(i) vs sin(r) useful? (It produces a straight line whose gradient gives the refractive index.)  
  *How can systematic errors be reduced when drawing normals? (Use a set square for accuracy.)  
  *How would your results differ if you used water instead of glass? (The refractive index would be smaller, so refraction would be less pronounced.)  
  *Why does Snell’s Law not apply when the angle of incidence is 0°? (The ray travels straight with no refraction.)