This is a class project is based on 2 evelopes being attached to a broom handle.

Question

This is a class project is based on 2 evelopes being attached to a broom handle. 1 evelope has a pinhole punched through it, the other is a number of cm away on the other end of the broom handle. This exercise is supposed to be performed sometime around high noon so there is full sun exposure.

Diameter of the Sun Activity (due at Stage 1)

Brief Overview of Activity: A pinhole can form an image in much the same way as a lens. Measuring the size of the Sun%u2019s projected image and the distance between the pinhole and the image, you will be able to calculate the diameter of the Sun.

Required Items: a friend to help you, a broom handle (or mop handle or long straight piece of wood of similar dimensions), a ruler (marked in centimeters), two envelopes, a pencil, masking tape, one stick-pin.

Number of Observations needed: 1

Timing of Observations: near noon on a bright sunny day

Procedure:

Preparation: Use the stick-pin to poke a small hole near the center of one of the envelopes. Mark a location near the top of the broom handle with masking tape (this is where your friend will hold the envelope with the pin-hole). Mark another location near the end of the broom handle with masking tape (this is where you will observe and mark the image). Carefully measure the distance between your two marked locations on your broom handle. Make your measurement to the nearest 0.1 centimeter and record here: _______ cm.

Observation: Gather your friend, marked broom handle, two envelopes, pencil, and then head outside. With your friend holding the envelope with the pin-hole at the upper marked position and you holding the other envelope at the lower marked location, align the broom handle such that a small faint image of the Sun%u2019s disk is seen on the lower envelope. You may find it convenient to actually sit on the ground for this procedure. With a pencil, carefully mark the location of opposite sides of the Sun%u2019s disk.

Calculation: From your marked envelope, carefully measure the size of the projected image of the Sun%u2019s disk to the nearest 0.1 centimeter and record here: ______ cm.

Next, use the relationship below to calculate the Sun%u2019s diameter in kilometers. Note that the distance to the Sun is 1.5 x 10 8 km.

      Sun%u2019s diameter in kilometers                     image diameter in centimeters

----------------------------------------- = --------------------------------------------------

Distance to the Sun in kilometers         distance between image and pin-hole in cm

Record your calculated value for the diameter of the Sun ___________ km

Part #1: Data and results from your diameter of the sun (attached) activity:

image diameter: _______ cm

distance from pin-hole to image: _______ cm

calculated diameter of the sun: _______ km

How does your calculated value for the diameter of the sun compare with its actual value? If the values are different, describe possible reasons for the difference. Can you think of any improvements that could be made to the procedure? (30 points)

Explanation / Answer

distance between two marked locations on broom handle = 100 cm

the size of the projected image of the Sun = 0.9 cm

using formula:
diammeter of sun/distance of sun = diameter of image/distance
=> x/1.5*100000000 = 0.9/100

=> x = 1350000 km


image diameter:0.9cm


distance from pin-hole to image: 100 cm


calculated diameter of the sun: 1350000 km

the actual value is 1391000 km

the variation in calculated size may be due to inaccuracies in the mesurement of diameter of image

Improvements might be to have better wquipment to measure the diameter of image and thus increase accuracy by improving the least count of mesurement

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