The method and the results are on the moon phases lab. Do the analysis yourself first, then check the answers below.
Quick answer: A shadow forms when an opaque object blocks straight-line light. These answers go with the grade 6 science lab on moon phases: the graph, the calculations, the uncertainties and the conclusion explained, for all 7 analysis questions.
The model answers use the sample measurements in the table. In addition, your own numbers will differ a little, but the shadow should shrink as the card moves away from the lamp, and the product should stay roughly constant.
10 × 100 ÷ 40 = 25 cm. The measured value is 25.2 cm, so it agrees within 1 %.
Question 2 Trend
The shadow height decreases as the card moves away from the lamp: from 50.5 cm at 20 cm down to 16.9 cm at 60 cm.
Question 3 Magnification
50.5 ÷ 10 = 5.05; 16.9 ÷ 10 = 1.69. Also, the shadow is 5 times the card at 20 cm but under 2 times at 60 cm.
Question 4 A constant product
20 × 50.5 = 1010; 30 × 33.8 = 1014; 40 × 25.2 = 1008; 50 × 19.8 = 990; 60 × 16.9 = 1014. The values are all about 1000 (10 × 100), so height is inversely proportional to d.
Question 5 Moon model
Ball between you and lamp: new Moon. Lamp at your side: first or last quarter. Also, lamp behind you: full Moon. Moreover, lamp at the other side: the other quarter.
Question 6 Sources of error
The lamp is not a point, so the shadow edge is blurred and hard to measure. In addition, the card may lean or the distance may be misread. Also, any two sensible reasons are accepted.
Question 7 Improvement
Use a smaller, brighter lamp or cover the lamp with a card with a tiny hole, and work in a darker room.
