Lenses Flashcards
What do converging/convex lenses do to parallel rays of light?
Cause them to be brought together (converge) at the principal focus.
What do diverging/concave lenses do to parallel rays of light.
Causes them to spread out (diverge).
What is the axis of a lens?
The line passing through the middle of the lens.
In converging lenses, what is the principal focus?
The point where rays hitting the lens parallel to the axis all meet.
In diverging lenses, what is the principal focus?
The point where rays hitting the lens parallel to the axis appear to all come from. Appear to meet up behind the lens.
What is the focal length?
The distance from the centre of the lens to the principal focus.
How are real images formed? Can the image be captured?
When light rays actually come together to form the image and it can be captured on a screen.
How are virtual images formed? Can the image be captured?
When lights rays from the object appear to be coming from a completely different place to where they’re actually coming from. It cannot be captured.
The more powerful the lens…
…the more strongly it converges the ray of light. Shorter focal length.
Which lens is positive and negative?
Converging lens - positive power
Diverging lens - negative power
How do you make a more powerful lens? Two ways
Make it with more strongly curved surfaces or changing the material.
Power of lens formula?
Power of lens = 1/f
