======Inverse Square Law with Light======


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**Alternative titles:** Light Intensity and Distance
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====Summary====                   
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====Procedure====  
  - Set up a lamp on a stand in a darkened room.  
  - Place a light meter at a distance of 30 cm from the lamp and record the reading.  
  - Move the meter to 60 cm and then to 90 cm, recording readings at each distance.  
  - Compare the values: intensity should fall in the ratio 1 : 1/4 : 1/9. 




====Links==== 
The Inverse Square Law - Saturday Morning Astrophysics at Purdue: 
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📄 The inverse square law with light - Institute of Physics: [[https://spark.iop.org/inverse-square-law-light]]\\


====Variations====
  * Use different types of light sources (e.g., LED, incandescent) and compare results.  
  * Measure at additional distances to refine the curve of 1/r².  
  * Repeat the experiment with a sound source and microphone to show the same principle with sound waves.  
  * Extend with a classroom analogy like the “butter gun” example, where spray thins out over greater distances.



====Safety Precautions====
  * Use only standard tungsten lamps, not unfiltered halogen lamps (to avoid UV exposure).  
  * Ensure power supplies and lamp holders are handled safely.  
  * Work in a controlled, darkened environment to avoid tripping hazards.




====Questions to Consider====
  * What happens to light intensity when the distance is doubled? (It decreases to one quarter.)  
  * Why does light spread out this way? (It radiates in straight lines and spreads over an area that grows with the square of the distance.)  
  * How does this principle connect to Newton’s idea of gravity? (Gravity also follows an inverse-square law with distance.)  
  * Can you think of other physical quantities that follow the inverse-square law? (Yes: sound intensity, radiation, and gravitational/electric field strength.)