Page 129 - SST Class 06

Direct and Slanting Rays the sunrays are vertical at the Equator than at

You have already studied about vertical and other latitudes. Areas around Equator receive
slanting rays. This phenomena happens because more heat than other latitude.
the earth is tilted on its axis and also because the Slanting and Vertical Rays of the sun on 21
earth spins about its axis. The fact that summers March, 21 June, 23 September and 22
are hot and winters cold is directly a result of December at Singapore 1°N latitude and Sao
vertical and slanting rays of the sun. When the Paulo (Brazil) centre 23½° S latitude.
sun shines vertically overhead, rays of the sun Vertical and slanting rays are not only true in the
gets concentrated over a small area giving more case of summers and winters, but also with
heat. On the other hand, slanting rays are spread respect to different times of the day. In the
over a wide area. This is the case in winter when mornings and evenings, slanting rays beat up
sunrays come through the atmosphere less atmosphere much less than at noon. As the day
directly. The atmosphere also absorbs some of advances at noon, the sunrays become more
the heat. Therefore, in winters, there are longer direct and then become slanting again and
hours of night and shorter hours of daylight. temperatures start falling towards evenings.
Duration of daylight in summer goes on increas- In the tropical zone especially at the Equator the
ing from 12 hours at Equator, 15 hrs at 40° N, 24 effect of vertical rays is felt more. In the temper-
hrs at 66½° N, 4 months at 78°51’ N and 6 ate latitudes only slanting rays are received.
months at 90°N. Because of angle of incidence,

Singapore 1°N

N S

89° 67.5° 89° 65.5°
Sao Paulo 23.5°
(Brazil)

S

N

90°

66.5° 43° 66.5°

Social Science-6 129