Now, before I say anything, this experiment doesn’t use actual gamma rays as they are dangerous and not allowed at school. Instead we will be investigating how the thickness of tracing paper affects the current produced from LDR (Light Dependant Resistor). This experiment is meant to mimic what will happen if we used gamma rays (the light ) and a different material (the tracing paper).
Firstly, let’s identify what the independent and dependant variables are:
Independent Variable – Thickness of tracing paper
Dependant Variable – Current in the circuit
Independent variable causes a change in Dependent Variable and it isn’t possible that Dependent Variable could cause a change in Independent Variable. So, the thickness of tracing paper causes a change in the current of the circuit.
Background light (meant to mimic background radiation), distance LDR is to light bulb, voltage, shroud, LDR, bulb, thickness and type of each individual tracing paper, ammeter, circuit and distance tracing paper is to LDR and bulb.
- LDR& circuit board
- Power supply
- Wire leads
- Lamp & holder
- Clamp stand, boss and clamp
- Small squares of tracing paper (roughly 5cm squared)
|Circuit set up for Physics IAA experiment|
3) Connect the LDR with its black paper tube or shroud in series with a milli-ammeter and then connect the other ends of the leads across the same two terminals on the power supply.
(this is where you should use your results and scientific knowledge)
Ultimately, the thicker the tracing paper, the lower the current is. This is due to the tracing paper blocking some light from reaching the LDR (just like metal can block some gamma rays reaching its destination). This caused the LDR to absorb less light and therefore produce a lower current in the circuit. The graph starts off steep showing the thickness of tracing paper affects the current the most in the first few layers, then starts to level out towards the end. This just proves that the first few layers of tracing paper block out the most amount of light from reaching the LDR, while the layers after that have not as big an impact.