Converging lenses
Light rays converge after refraction through the lens
Characteristics of converging lenses
Lens is thickest in the middle and thinnest at the ends
Diverging lenses
Light rays diverge after refraction from the lens
Characteristics of diverging lenses
Thinnest in the middle and thickest at the edge
Optical centre
The point at the exact centre of the lens
Principal focus
The point on the principal axis of a lens where the light rays parallel to said axis converge after refraction (principal focus on the same side of the lens as the incident rays is called the secondary principal focus/F’)
Difference between curved mirrors and lenses
- In mirrors, light reflects, but in lenses, light refracts
- Images on the same side of the mirror are real but on the same side of the lens are virtual
- Images on the other side of the mirror are virtual but on the other side of the lens are real
When is the height of an object/image a positive value?
When measured upwards
When is the height of an object/image a negative value?
When measured downwards
When is the distance of an object a positive value?
It is always a positive value
When is the distance of an object a negative value
It is never a negative value
When is the distance of an image a positive value
When it is a REAL image (image is on the opposite side of the object)
When is the distance of an image a negative value
When it is a VIRTUAL image (image is on the same side as the object)
When is the focal length a positive value
When we are working with converging lenses
When is the focal length a negative value
When we are working with diverging lenses
When is magnification a positive value
When the image is upright
When is magnification a negative value
When the image is inverted
