Name Date Period I-ight 0n the Spherical Earth Purpose To model how lightfrom the sun is distributed over the surface of the Earth.

Procedures *Be sure that each person has a chance to hold and move the paper. EBe sure NOT to stand between the light source and the globe.

I . Be sure that the globe has the North Pole at the top and that the equator is horizontal.

2. Hold the piece of paper between the globe and the light source so that it hangs vertically and is perpendicular to the direction the light is coming from. Hold the paper about 20 cm from the globe so that a fairly clear square of light is projected on the center of the globe.

3. Slowly move the piece of paper side to side so that the paper hangs vertically and is perpendicular to the direction the light is coming from. Do not tilt or turn the paper. Keep the patch of light along the equator. Draw and describe what happens to the shape and brightness of the light patch in different positions along the equator. Draw on the globe picture and describe in the space below. (NP = North Pole. EQ = Equator, SP = South Pole) Picture of Globe Description:

Answer the following: (Use complete sentences for b and c) a. On the picture above, label which patch of light represents morning sun, midday sun, and late afternoon sun. b. The hole in the paper allovrs a certain amount of light to pass through and is a sampling of the total light that would reach the globe. That amount of light is spread differently over differenf parts of the glcbe. At which time(s) of day does the light patch irave the greatesr intensity?

Least intensity?

c. At which time(s) of day does the light reach the surface ar the highest angle (sun highest in the skY)?

Lowest angle (sun lowest in the sky)? 4. Slowly move the piece of paper up and down so that the paper hangs vertically and is perpendicular to the direction the light is coming from. Draw and describe what happens to the shape and brightness of the light patch as it is in different positions north and south of the equator. Draw on the globe picture and describe in the space below.

Picture of Globe Description: NP (high latitude)

(low Iatitude)

SP (high latitude) Answer the following with complete sentences: a. How does the size of the light patch change from low latitude (near the equator) to high latitude (near the poles).

b. How does the intensity of the light patch change from low latitude (near the equator) to high Iatitude (near the poles).

c. The size and intensity of the Iight patch is affected by the angle at which Iight reaches the surface. Does light reach the surface at high angles (sun high in the sky) near the poles or the equator?

Does light reach the surface at low angles (sun low in the sky) near the poles or the equator?

Analysis Ouestions 1) Based on your observations in this lab, what is a reason the middle of the day is usually warmer than morning or evening? Refer to the intensity and to the angle of the light.

2) Based on your observations, why is the equator warmer than the poles? Refer to the intensity and to the angle of the light.