Lenses and Images Flashcards
How do lenses form images?
By refracting light and changing its direction
What are the 2 main types of lens?
Converging
Diverging
What does a converging lens look like?
It’s convex
It bulges outwards
(Like and ellipse with pointy ends)
Like this: ()
What does a converging lens to do parallel rays of light?
Makes them converge at the principal focus
What does a diverging lens look like?
Concave
Like this: )_(
What is the axis of a lens?
A line passing through the middle of the lens
What is the principle focus of a converging lens?
Where rays hitting the lens parallel to the axis all meet
What is the principle focus of a diverging lens?
The point where rays hitting the lens parallel to the axis APPEAR to all come from - you can trace them back until they all appear to meet up at a point behind the lens
What’s the focal length?
The distance between the centre of the lens and the principle focus
How many principle focus points are there. Where?
There’s a principle focus on each side of the lens
What is a real image?
Where light from an object comes to form an image on a ‘screen’ - like the image formed on the eye’s retina.
What is a virtual image?? Give an example
When rays are diverging, so the light from an object appears to be coming from a completely different place. When you look in a mirror you see a virtual image.
What kind of image do you get looking through a magnifying glass?
Virtual - the image looks bigger than it it
What 3 things do you use to describe an image?
Size compared to object (Magnified / Diminished)
Upright / Inverted
Real / Virtual
