Placing images with thin lenses

Science · Waves, Light & Sound · ages 19-20

Name ______________________ Date ____________

A real image can be caught on a screen.
Circle one: True False
What is the thin lens equation?
- f equals do plus di
- One over f equals one over do plus one over di
- m equals minus di over do
What does a ray through the lens centre do?
- It bends to the near focus
- It continues straight on
- It reflects backwards
An object sits inside f of a converging lens. What image appears?
- Real inverted and small
- No image at all
- Virtual upright and enlarged
do is 30 cm and di is 15 cm. Give the magnification.
Answer: ______________
What does the lensmaker equation connect?
- Focal length to index and curvatures
- Image size to screen distance
- Brightness to lens thickness
f is 10 cm and do is 30 cm. Give di in cm.
Answer: ______________
A student projects a virtual image onto a screen across the room.
Circle one: True False

Answer key

For grown-ups. Fold this page away before handing over the rest.

True · Real means rays truly meet where the screen sits.
One over f equals one over do plus one over di · Focal length links to both distances through reciprocals.
It continues straight on · Centre rays pass undeviated in the thin approximation.
Virtual upright and enlarged · A magnifier gives a virtual upright enlarged image.
-0.5 · Minus 15 over 30 is minus 0.5.
Focal length to index and curvatures · Glass index and surface curves fix f.
15 · One over di is one over 10 minus one over 30, giving 15.
False · Virtual images never land, so no screen can catch one.