thin converging lenses Flashcards
Lens definition
A lens is a piece of clear plastic or glass with curved surfaces for concentrating (converging) or dispersing (diverging) light rays. It is widely used in cameras, spectacles, projectors
Types of lenses
- Converging: thicker in the middle than at the edges
- diverging: thinner in the middle than at the edges
How does a lens refract light?
- A lens can be thought of as a set of small prisms
- parallel light rays will be incident on different sections of the lens at different incident angles
- light rays refract upon entry and exit of each section. Light rays will bend the most near the edges of the lens, while less or no refraction occurs in the middle section
- a converging lens causes all emerging rays to converge at a point
- a diverging lens causes incoming light rays to spread out
Principal Axis definition
The line which passes through the center of the lens and which is perpendicular to the plane of the lens
Optical centre definition
The point on the principal axis that is the midpoint between the surfaces of the lens
Focal length
The distance between the optical centre and the principal focal point
Principal focal point/ principal focus
The point on the principal axis where all the rays parallel to the principal axis meet after passing through the length
Focal plane
The plane perpendicular to the principal axis on which all parallel rays meet after passing through the lens
Observation for thin converging lens
- For real images, the further away the object is from the lens, the closer the image will be to the lens and vice verse.
- Image characteristics real is always tied to inverted; virtual is always tied to upright. ( virtual images mean that the image cannot be projected on the screen )
- Real images are always on the opposite side of the lens as the objects, virtual images are always on the same side of the lens
