7 - Pinhole Tube and Telescope
Instructions: Follow Parts I–IV to explore simple optics. Complete the questions (Q1–Q35) on a separate piece of paper and the provided Observing Log Sheets. Work with your group but submit your work separately. Due: in one week, at class time
Part I: Pinhole
Purpose: To build a pinhole tube and use it to make a terrestrial measurement.
Materials: 2 nesting cardboard tubes straight pin aluminum foil ruler (may be on protractor) tracing paper measuring tape
rubber bands 200-watt, unfrosted light-bulb lamp 2 stands clamps calculator
Pre-lab Question—What do you think?:
On your separate piece of paper, write your best estimate, based on your personal experience.
Q1) How many Sun-diameters fit between Earth and the Sun?
Procedure:
1. Filament Size: Measure the length of the filament (tightly coiled piece of wire) in the bulb (line XY in Figure 2). To make the measurement, place the ruler in front of the bulb. Close one eye and record the length. The filament is slightly curved; therefore, measure the straight-line distance between the two ends of the filament. Measure and record the length with the ruler behind the glass. Average these two values.
Q2) Record and label the length of the filament (XY) in centimeters (cm)
Figure 1: Diagram of the relationship between the filament length (XY), pinhole-to-filament distance (D), length of pinhole tube (L), and length of image of the filament on the tracing paper (AB).