School of Physics Lecture Demonstration Manual

Hc-5 Absorption of Radiation by Black and White Surfaces

Published: Monday 13 March 2006 - Updated: Monday 28 March 2011


To demonstrate the relative absorption of black and white surfaces.



Click on pictures to enlarge.

Absorb of Radiation Diagram


Two thermoscopes have been constructed, one having a black surface, the other white. The pressure inside is reduced from atmospheric and equalized by the connecting tubes and valve A. The valve is then closed so that the two thermoscopes are independent. On turning on the 150 W spotlight a difference in fluid height indicates a difference in pressure between the two tubes due to different temperatures. This indicates that the black surface has absorbed more heat than the white surface.

Safety notes

Electrical Safety 

Fire/Burn Safety 


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