Quill holds a magnifying glass up to the window. The lens bulges: it is fat at the center and thin at the rim, and the sunlight passing through it narrows to a bright spot on the desk.
A lens is a shaped piece of clear glass or plastic that light passes through. This lesson sorts lenses into the two kinds by their shape.
Run your eye across a lens from edge to edge.
Some lenses are thicker at the middle than at the edges. That shape is convex, the same shape word you met on mirrors.
Other lenses are thinner at the middle than at the edges. That shape is concave.
So the sort is one read: thicker at the middle means converging, and thinner at the middle means diverging.
Watch the near miss. A concave mirror brings rays together, but a concave lens spreads them apart.
The mirror bounces light off its caved-in face; the lens passes light through its thin middle. Same shape word, opposite jobs.
Why does a lens redirect light at all? Light refracts where it enters the glass and again where it leaves, because the glass is a new medium. The lens shape decides where those refractions send the rays.
Romilly picks up an eyeglass lens. Its middle is noticeably thinner than its rim. Is this lens converging or diverging?
The sort is one read: compare the middle's thickness with the edges' thickness.
This lens is thinner at the middle than at the edges.
A lens that is thinner at the middle spreads rays apart.
The lens is diverging.
Stellan compares two objects: a concave makeup mirror and a concave eyeglass lens. Which one spreads light rays apart?
The mirror works by reflection off its caved-in face: a concave mirror brings rays together.
The lens works by light passing through: a concave lens is thinner at the middle.
A lens that is thinner at the middle spreads rays apart.
The concave lens spreads the rays apart; the concave mirror does the opposite job.
A camera lens is thicker at its middle than at its edges. Is this lens converging or diverging?
An eyeglass lens for nearsightedness is thinner at its middle than at its edges. Is this lens converging or diverging?
A door peephole holds a small lens thinner at its middle than at its edges. Is this lens converging or diverging?
A projector lens bulges on both faces, fattest at its center. Is this lens converging or diverging?
A camper's fire-starter lens has a rim that is its thinnest part. Is this lens converging or diverging?
A lens flat on one face caves inward on the other, so its center is its thinnest part. Is this lens converging or diverging?
Four lenses are laid on a tray. Which one is converging?
Parallel light rays pass through a lens that is thinner at its middle than at its edges. What do the rays do after the lens?
Thora has a concave makeup mirror and a concave eyeglass lens, and she sends three parallel light rays at each. Which statement describes what happens?