Compare converging and diverging lenses, then move an object to discover why a convex lens does not always produce the same image.
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A lens transmits and refracts light at its surfaces. It is not a curved mirror. In air, a typical convex lens is thicker at the centre and converges parallel rays; a typical concave lens is thinner at the centre and diverges them. The surrounding medium matters.
For a thin converging lens, a ray parallel to the axis leaves toward the far focus. A ray through the optical centre continues approximately straight. Where actual rays meet is the image point. Repeat for other points to build an image. Dashed backward extensions are not actual light travelling backward.
For an object beyond f, the ideal thin-lens image is real and inverted. Beyond 2f it is reduced; at 2f it has equal size; between f and 2f it is enlarged. Inside f it is upright, enlarged and virtual—the magnifying-glass arrangement. At f there is no finite image in the ideal model.
For a real object, an ideal diverging lens in air gives an upright, reduced virtual image on the object side. A focal point on a drawing does not mean all actual rays pass through it. Check whether the convergence is real or inferred from extensions.
Relate focal length and object position to real/virtual, upright/inverted and enlarged/reduced images.
INTEGRAL PHYSICS · Lab demonstration
Compare the projected image with the virtual image. Connect object position, orientation and a screen’s ability to catch the image.
Use the Lens screen to move the object and compare converging and diverging lenses.
Predict the image before moving the object. Test whether a screen can catch it, then explain the difference between real and virtual.
Sketch one before-and-after comparison. Label what you changed and what stayed the same. Use the lesson’s vocabulary to explain the result.
Ideal thin lens in air; paraxial rays. Distances are model units. Solid lines show light paths; dashed lines are backward extensions. F marks a focal point. At f, outgoing rays are parallel.
A real image forms where actual rays meet. Can it be caught on a screen? State yes or no and explain your reasoning.
Think about a projector.
Actual rays arrive at the image location.
A converging lens has f = 6 cm and object distance 3 cm. State real or virtual and explain your reasoning.
The object lies inside the focal length.
The image is upright, enlarged and virtual.
Why would a diverging lens alone not make a real image of a distant scene on a sensor?
For a real object, an ideal diverging lens makes outgoing rays diverge. The virtual image lies on the object side and cannot be caught directly on a sensor behind the lens.
Image size and orientation depend on object position. A camera can form a reduced real image; a magnifying glass can form an enlarged virtual image.
Commit to an answer, then use the feedback to check your reasoning.
