Romilly holds a magnifying lens of focal length 10 cm just 5 cm above a stamp. Through the glass she sees the stamp enlarged and right-way-up. No card behind the lens catches anything at all.
Last construction, the object stood beyond the focal point. Slide it inside the focal point and the same two rays tell a different story: the beam spreads, and the image has to be traced back.
Start with the skeleton: the lens, both focal dots 10 cm out, and the stamp standing upright just 5 cm from the lens, INSIDE the near focal dot.
From the stamp's tip, draw ray 1, arriving parallel: it bends at the lens and exits through the far focal point, heading downward.
From the same tip, draw ray 2, through the exact center: it continues straight, also heading downward, but at a steeper slant.
Follow the two refracted rays to the right: they spread apart. They never cross on the far side.
So trace both refracted rays straight back to the left, as dashed lines.
The dashed trace-backs meet on the stamp's side of the lens, higher than the stamp's tip and farther from the glass.
Only traced-back lines meet there, so the image is virtual: no screen can catch it.
You see it by looking into the lens from the other side: the spread rays enter your eye as if they came from the big upright stamp.
That is the magnifying glass, drawn: object inside the focal point, image virtual, upright, enlarged.
Run the construction for Romilly's stamp: 5 cm from a convex lens of focal length 10 cm. State each step and read the image.
Draw the skeleton: lens, principal axis, focal dots at 10 cm, the stamp upright at 5 cm, inside the near dot.
Ray 1 from the tip arrives parallel and exits through the far focal dot.
Ray 2 from the tip runs straight through the exact center, at a steeper downward slant.
The two refracted rays spread apart on the far side, so trace both straight back as dashed lines.
The trace-backs meet on the stamp's side, higher and farther out than the tip; draw the image arrow there.
The image is virtual, upright, and enlarged, on the stamp's side of the lens.
Quill slides the same stamp out to 15 cm from the same lens, past the focal dot, and redraws. What changes in the construction's ending?
At 15 cm the stamp sits beyond the focal point.
The same two rays now actually cross on the far side of the lens, below the principal axis.
An actual crossing needs no trace-back: the image is real and inverted.
The ending flips to the earlier construction's: a real, inverted image on the far side.
In the magnifier construction, the two refracted rays spread apart after the lens. What is the next drawing step?
Where does the magnifier construction place the image of the stamp's tip?
Stellan says: 'No card placed behind this lens will ever catch the stamp's image.' Is Stellan correct?
A sticker sits 6 cm from a convex lens of focal length 12 cm. The refracted rays from its tip spread apart, and their dashed trace-backs meet on the sticker's side. Which description of the image is correct?
Which sketch correctly constructs the image of a stamp inside the focal point of a convex lens?
In the finished magnifier drawing, the lines that meet at the image are dashed. What does that say about the image?