Lenses and ray diagramsEdexcel A-Level Physics: Mind map

Exam questions on Lenses and ray diagrams

1. A student wants to find the focal length of a thin converging lens. She holds the lens so that it forms a sharp image of a distant window on a white screen and measures the distance from the lens to the screen. The distance is 0.125 m.
   Explain why the distance from the lens to the screen is equal to the focal length of the lens.2 marks
2. A diverging lens of focal length 0.40 m is used to view a small illuminated object placed on its principal axis. A student plans to locate the image by drawing a scale ray diagram of the arrangement.
   Describe how the student should use two rays from the top of the object to locate the top of the image.2 marks
3. An optician combines two thin lenses in contact on a common principal axis. The first is a converging lens of focal length 0.20 m. The second is a diverging lens of focal length 0.50 m (magnitude). A parallel beam of light is sent through the combination along the axis.
   Calculate the power of each lens and the power of the combination.3 marks