Physics – 3.2.3 Thin lenses | e-Consult
3.2.3 Thin lenses (1 questions)
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Calculation: Using the lens formula 1/f = 1/u + 1/v, where u = 30 cm and v = 40 cm, we have:
1/f = 1/30 + 1/40 = (4 + 3)/120 = 7/120
Therefore, f = 120/7 cm, which is approximately 17.14 cm.
Diagram: The ray diagram should show two rays from the object. One ray passes through the focal point. The other ray is parallel to the principal axis and refracts through the focal point. The intersection of these two refracted rays forms the image. The image is on the same side of the lens as the object, and it is inverted.
Labels: The diagram must include labels for:
- Object (o): Represented by a small shape.
- Principal Axis: A horizontal line passing through the optical centre.
- Focal Length (f): Marked with dashed lines extending from the focal point.
- Focal Point (F): The point where parallel rays converge.
- Image (i): Represented by a small shape.
- Object Distance (u): The distance between the object and the lens (30 cm).
- Image Distance (v): The distance between the image and the lens (40 cm).