1)What is latitude of subsolar point (SSP) or declination? (where sun’s rays are vertical)

2. At what latitude will sun’s rays be oblique / tangent?

3. Where is Circle of Illumination? (separates light and dark halves)

December Solstice

1.SSP = 23.5^{o}S

2. tangent rays at 66.5^{o}N, 66.5^{o}S

3. C.I. is tangent at 66.5^{o}N, 66.5^{o}S (such that all latitudes above 66.5N are in 24 hour darkness; all latitudes above 66.5 S are in 24 hour daylight)

March Equinox

1.SSP= 0°

2. tangent rays at 90^{o}N, 90^{o}S

3. C.I. is tangent at 90°N, 90°S

June Solstice

1. SSP = 23.5^{o}N

2. tangent rays at 66.5^{o}N, 66.5^{o}S

3. C.I. is tangent at 66.5^{o}N, 66.5^{o}S (such that all latitudes above 66.5 N are in 24 hour daylight and all latitudes above 66.5 S are in 24 hour darkness)