Carolina Power House Kit - Manual (Page 5)

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Why it gets cold in winter
If you want to save energy with your
Power House and, more importantly, in an ac-
tual building, the outside temperature will have
an important role to play. In the winter, you will
need a lot more heat than in summer, because
it is cold. But why is it cold, actually?
You will need
Flashlight, yarn or string, tape, scissors, graph
paper, colored marker
Experiment
1. Cut off a piece of yarn about 30 cm in length.
Tape one end to the center of a sheet of graph
paper, and tie the other end to the flashlight.
2. Shine the light straight
down on the paper
from above with the
yarn pulled taut, and
use the marker to
draw a line around the
spot of light.
3. Now shine the light at an angle from the side
from the same distance, and mark the bright
spot again.
4. Count the squares inside the two outlined
areas and compare.
Explanation
When you shine the light at a slant, the bright
spot is much larger, but also less bright. That is
due to the fact that the quantity of light from
the flashlight now has to be distributed across a
much larger surface area. Any single individual
square, then, gets less light.
It’s similar with sunshine. In the winter,
when the sun stands closer to the horizon than
in winter, its light and warmth are distrib-
uted across a larger area of Earth, so
any individual spot gets less of it
and is therefore cooler.
Light rays take a detour
Normally, as Experiment 52
showed, light rays will stubbornly run
straight ahead and won’t turn any corners.
There are a few tricks, though…
You will need
Solarium annex cover, aluminum foil, white
paper
Experiment
1. Look at the transparent annex cover at a
slant. It is reflective. So you will see things, for
example, that are behind you and to the side.
2. If you hold the paper and cover sheet in the
sun as shown in the illustration, you can create
a bright spot on the paper or on a shaded wall.
3. Bend the edges of the sheet slightly toward
the sun. How do the shape and size of the spot
change?
4. Now bend the edges of the sheet away from
the sun. What effect does that have on the
spot?
5. Place smooth aluminum foil behind the
sheet, with the shiny side toward the sheet, and
repeat the experiments. Now the spot is some-
what brighter.
Explanation
Smooth surfaces reflect light rays — in other
words, they change the direction of movement
of the rays. That fact lets you use the sheet to
look around corners, for example, or to direct
the sunlight onto a shaded wall. It works even
better with the shiny aluminum foil, which re-
flects more light — the cover, after all, lets most
of the light through. Mirrors work best of all.
With a smooth sheet, incoming parallel light
rays keep traveling in parallel manner after
being reflected, just in a different direction. But
if you bend the sheet, you also change the man-
ner in which the rays of light are reflected back.
As shown in the illustration, you can use this
technique to concentrate the rays on one spot
or to pull them apart.
EXP.
54
EXP.
55