Please provide a rating, it takes seconds and helps us to keep this resource free for all to use
Welcome to our Physics lesson on Day and Night, this is the tenth lesson of our suite of physics lessons covering the topic of Sun and Planetary Motion, you can find links to the other lessons within this tutorial and access additional physics learning resources below this lesson.
"Day" represents the time in which a region of Earth is directly exposed to sunrays. Night is the opposite, i.e. a region is either illuminated indirectly from the Sun (through Moon surface that reflects the sunrays on Earth) or by means of other light sources (usually artificial, such as electric bulbs).
All locations on the equatoralways have equal durations of day and night as the sunlight always falls on them at the same angle. On the other hand, the further North (or South for southern hemisphere) a location is, the more variation there is between day and night duration at solstice(s). For example, in locations near the North Pole, no sunset occurs for several months during summer solstice while the sun does not rise for several months (during winter solstice) on locations near the South Pole in the same period of year.
A certain location receives 1400 W/m2 energy during the summer solstice, where the angle of incidence is normal to the ground. How much solar energy per unit area does the same location receive in winter solstice if the deflection angle to the vertical in that moment is 72° (cos 72° = 0.309, sin 72° = 0.951).
We denote by E0 the maximum energy falling in the given location (E0 = 1400 W/m2). When sunrays fall normal to the ground, the effect of energy transfer is at its' maximum. Thus, if we consider the incidence angle as 0° to the normal, we must multiply the value of energy by cos 0°, as this gives the maximum value (cos 0° = 1). When the angle of incidence becomes 72°, we must therefore multiply the previous value of energy by cos 72° to find the amount of solar energy falling on that location in winter. Hence, we have
You have reached the end of Physics lesson 22.2.10 Day and Night. There are 10 lessons in this physics tutorial covering Sun and Planetary Motion, you can access all the lessons from this tutorial below.
Enjoy the "Day and Night" physics lesson? People who liked the "Sun and Planetary Motion lesson found the following resources useful:
Please provide a rating, it takes seconds and helps us to keep this resource free for all to use
We hope you found this Physics lesson "Sun and Planetary Motion" useful. If you did it would be great if you could spare the time to rate this physics lesson (simply click on the number of stars that match your assessment of this physics learning aide) and/or share on social media, this helps us identify popular tutorials and calculators and expand our free learning resources to support our users around the world have free access to expand their knowledge of physics and other disciplines.