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The sphere is centered at the origin with a radiation source. A vector S represents the radius of the sphere labeled, direction (theta, phi). An angle between the vertical axis and the vector R is labeled, theta. A line is projected on the x-y plane from the vector S. An angle between the projected line and the x-axis is labeled, phi. The polar coordinates of the sphere are as follows:

Theta equals zero at the z axis.

Theta equals 90 degrees and phi equals 90 degrees at the positive y axis.

Theta equals 180 degrees at the negative z axis.

Theta equals 90 degrees and phi equals 270 degrees at the negative y axis.