# Physics 3 - 13.4 Mirrors and Lenses

Ray Diagrams

• A horizontal line passing through the centre of the lens is called the principal axis
• A ray of light entering the lens parallel to the principal axis will be refracted through the principal focus of the lens, f
• A ray through the principal focus mergers parallel to the principal axis
• A ray through the centre of lens passes straight through without refracting
• Rays of light from infinity are parallel

Magnification

• A converging lens acts as a magnifying glass when the object is closer than its focal length
• The thing that you look at is called the object. What you can see is the image:

magnification = image height / object height

An image is described by its magnification, whether it is upright or inverted relative to the object and whether it is real or virtual:

• a real image is formed when rays…

## Similar Physics resources:

See all Physics resources »See all Light and Optics resources »

# Physics 3 - 13.4 Mirrors and Lenses

Ray Diagrams

• A horizontal line passing through the centre of the lens is called the principal axis
• A ray of light entering the lens parallel to the principal axis will be refracted through the principal focus of the lens, f
• A ray through the principal focus mergers parallel to the principal axis
• A ray through the centre of lens passes straight through without refracting
• Rays of light from infinity are parallel

Magnification

• A converging lens acts as a magnifying glass when the object is closer than its focal length
• The thing that you look at is called the object. What you can see is the image:

magnification = image height / object height

An image is described by its magnification, whether it is upright or inverted relative to the object and whether it is real or virtual:

• a real image is formed when rays…