The volume of the dish is given by formula_16 where the symbols are defined as above. This can be compared with the formulae for the volumes of a cylinder formula_17 a hemisphere formula_18 where formula_19 and a cone formula_20 formula_21 is the aperture area of the dish, the area enclosed by the rim, which is proportional to the amount of sunlight the reflector dish can intercept. The area of the concave surface of the dish can be found using the area formula for a surface of revolution which gives formula_22. providing formula_23. The fraction of light reflected by the dish, from a light source in the focus, is given by formula_24, where formula_25 formula_26 and formula_27 are defined as above.