School of Physics Lecture Demonstration Manual

Ok-3 Inverse Square Law

Published: Tuesday 05 June 2007 - Updated: Monday 28 March 2011


To demonstrate the inverse square law



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A light source casts a shadow onto a reference grid. The CCD camera is attached at a fixed distance from this grid and focused on the image. The source to grid distance is adjusted to 20cm and the object moved to 10 cm from the source so that the shadow covers exactly 4 squares. The voltage to the light source is adjusted so as not to produce flaring in the camera image. If the distance between the source and grid is doubled the shadow is seen to now cover 16 squares.

Safety notes

Electrical Safety 


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