# Homework 2. Phases

 Name: ________________________ Due 9/05 ID Number: ________________________

For this assignment you need a ball or some other roughly spherical object; for example, a balloon, an orange or even an apple. You also need a source of light, such as a desk lamp, which you can move around. Ideally, the light should have a small transparent bulb and cast clear sharp shadows. If you are using a lamp with a straight fluorescent bulb try placing it far away so it casts a relatively sharp shadow. If you are using a lamp with a shade, remove the shade.

## I. Phases in Miniature

Place the ball on the desk in front of you and position the light as indicated. Then sketch the appearance of the ball within the outline provided, doing your best to show which side is illuminated, whish side is in shadow, and where the dividing line between light and shadow falls. (Don't worry about being artistic -- just try to show things as clearly as you can.)

 1. Place the light to the left of the ball, and somewhat behind it. 2. Place the light well behind your position, and just slightly to your right. 3. Place the light directly above the ball.

## Phases in the Sky

On two or three reasonably clear nights this week, go outside in the evening and locate the Moon in the sky. The Moon will be up at sunset throughout the next week or so; but if it's party cloudy you may have to wait a few minutes for the clouds to drift by. If we get a run of bad weather I will post a few images of the Moon on the class web pages; you can use them instead, but it's much more fun to actually go out and look at the sky!

Once you've found the Moon, make a quick sketch of it just like you did of the ball. Write the date and time in the spaces provided. Finally, make a guess where the light source (the Sun) is in relation to the Moon.

 1. Date: ___________________________________________ Time: ___________________________________________ Sun's position: ____________________________________ _________________________________________________ 2. Date: ___________________________________________ Time: ___________________________________________ Sun's position: ____________________________________ _________________________________________________

## Extra Credit

 Find the Moon in the daytime sky and hold the ball up next to it. Sketch the phases of both. Do they show the same phase? Moon Ball