A student has a converging (convex) lens and needs to determine its focal length. Plan an experiment that will enable the student to measure an accurate value for the focal length f of the lens. The focal length f of a lens can be calculated using the equation: f = uv / (u + v) where u is the distance between an object and the lens and v is the distance between the focussed image of the object and the lens. Fig. 4.1 shows some of the apparatus available. [Figure 4.1] The lamp is connected to a power supply and can be switched on and off as required. Write a plan for the experiment. You are not required to do this experiment. In your plan you should: • list any additional apparatus needed • draw a diagram of the arrangement of the apparatus, labelling u and v • explain briefly how to do the experiment • state the steps taken to obtain a sharp, focussed image • explain how to use your readings to determine f.

1. A student has a converging (convex) lens and needs to determine its focal length. Plan an experiment that will enable the student to measure an accurate value for the focal length f of the lens. The focal length f of a lens can be calculated using the equation: f = uv / (u + v) where u is the distance between an object and the lens and v is the distance between the focussed image of the object and the lens. Fig. 4.1 shows some of the apparatus available. [Figure 4.1] The lamp is connected to a power supply and can be switched on and off as required. Write a plan for the experiment. You are not required to do this experiment. In your plan you should: • list any additional apparatus needed • draw a diagram of the arrangement of the apparatus, labelling u and v • explain briefly how to do the experiment • state the steps taken to obtain a sharp, focussed image • explain how to use your readings to determine f.[6]

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