Measure and note the length $H$ shown in Fig. 4.2.
Measure and record the shadow length $h$ shown in Fig. 4.3.
Suggest why it would be hard to measure the shadow length accurately.
Enter your value of $h$ from (b)(i) into the table in Fig. 4.4.
On Fig. 4.5, draw a graph of $h$ on the y-axis against $d$ on the x-axis. Begin both axes at the origin. Add the smooth curve of best fit.
Use your graph to find $h_{40}$, the value of $h$ when the object is $40.0\text{ cm}$ from the centre of the lamp.
The student states that $h_{40}$ is connected to the object's length $H$ by $h_{40} = 2H$. Calculate the length $H$ of the object using this equation.
Compare the value of $H$ obtained in (d)(ii) with the value you measured in (a). State whether your results support the student’s suggestion and explain your answer with reference to the results.
Extend your graph to predict the shadow length $h_{20}$ when $d = 20.0\,\text{cm}$.
The student says that the distance $d$ should not be less than 10.0 cm. Give one reason why this is a sensible suggestion.
$D$ was kept constant throughout the investigation. Suggest why.