# In-Class Activities

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Published 2022-09-10

# 5.5 In-Class Activities

In this activity, you will estimate the power of the Sun by using your feelings and performing a simple calculation.

First recall the feeling of standing under a hot sun. If it is bright and sunny now, go out and experience it for a while!

Position yourself close to a 100W incandescent light bulb. Cover your eyes with a blindfold or solar filter spectacles.

Ask one of your group-mate to switch on the bulb and move it towards you slowly.

Signal "stop" when the heat from the bulb feels like the heat from the hot sun.

Ask another group member to measure and record the distance from the bulb to you.

Repeat the experiment.

The power of the radiation from Sun and the light bulb is related to the intensity you feel by

\text{Intensity}=\frac{\text{Power}}{4\pi r^{2}}

where r is the distance between the light source and the detector (you!).

Discuss the above equation in the geometrical sense.

How far is the Sun?

Estimate the power of the Sun with your data.