What are the two types of lenses?
- Converging lens (Convex)
- Diverging lens (Concave)
What are converging lenses?
- They are convex lenses.
- They make parallel light rays converge/meet at a particular point.
- The lens is thick in the middle and thin at the ends.
What are diverging lenses?
- They are concave lenses.
- They make parallel light rays diverge after going through it.
- The lens is thin in the middle and thick at the ends.
Images formed by converging lenses
- As long as the object is outside the focal point, the image is real and inverted.
- When the object is inside the focal point, the image is virtual and upright.
- When the object is at 2F, the image formed is the same size as the object.
List down formulas to find Linear magnification, m
How are images formed in our eye?
- Light falling on object is reflected in all directions.
- Some reflected rays enter the eye.
- These light rays are bent (refracted) by the cornea, vitrous humor, lens, etc.
- Bent light rays meet on the retina.
- An inverted image is formed.
- Images on retina creates impulses, which will travel to the brain by sensory neurones.
- Brain interprets impulses so that the viewer sees the object right way up.
Name the two types of eye defects.
- Long-sight - can see far objects clearly, but near objects appear blur. (corrected by converging lens)
- Short-sight - can see near objects clearly, but far objects appear blur. (corrected by diverging lens)
- Changes of lens shape
- When I try to focus on a distant object, my lens become thin
- When I try to focus on a nearby object, my lens become fat