33.4 - Interactive problem: image with a diverging lens
This simulation lets you experiment with a diverging lens. You can drag the object
toward and away from the lens, and note how the image changes. Also note which
properties of the image remain consistent.
You can press “Show rays” to use the simulation to create a ray diagram. Pressing
“Hide rays” turns off the rays.
33.5 - Sample problem: object outside the focal point of a converging lens
As shown above, the penguin is between the focal point and a distance twice the focal length. What kind of image will result? Once you know
the result, can you think of any application that relies on a configuration like this?
Strategy
Use ray tracing to establish the nature of the image.
Diagram
Step-by-step solution
- Ray 1 starts parallel to the principal axis from the head of the penguin, refracts and passes through the focal point on the far side of the
lens. - Ray 2 passes through the center of the lens without changing direction.
- Ray 3 passes through the focal point on the near side and refracts at the lens to be parallel to the principal axis on the far side.
The result is an inverted image that is larger than the initial object. It is a real image, since light rays pass through the position of the image,
and they would create a projected image on a screen placed there.
Above, we also asked: What might be an application that relies on a configuration like this? A movie theater projector is one example. The
audience views enlarged, real images on the screen. Light is projected through the film, creating a luminous object from a tiny likeness, and
then passes through a projection lens to be magnified. The real image appears on the movie screen. The “object” is upside down on the film,
so when the lens inverts the image, it appears upright to the audience.