A convex lens is fatter in the middle, and that extra glass bends parallel light inward until it crosses at a single point. Slide an object nearer or further and the same lens can shrink it, flip it, or blow it up.
A converging lens refracts a parallel beam of light to a single point, the principal focus, a distance called the focal length from the lens. Where the object sits relative to the focal point decides whether the image is real or virtual, larger or smaller, upright or inverted.
A converging (convex) lens refracts a parallel beam of light to a single point called the principal focus. The focal length is the distance from the centre of the lens to the principal focus.
A real image can be formed on a screen and is inverted. A virtual image cannot be projected and is upright.
Move the object along the bench and watch the rays cross to build a real image, or spread to form a virtual one.
Four quick checks. Each correct answer earns XP and lights this skill on your star map.
A thin converging lens acts on a parallel beam of light by...
The focal length of a lens is the distance from the centre of the lens to the...
A real image formed by a lens is one that...
A converging lens is used as a magnifying glass when the object is placed...
The same lens gives very different images depending on the object distance compared with the focal length.
| Object position | Image formed |
|---|---|
| Beyond 2F | Real, inverted, smaller than the object |
| At 2F | Real, inverted, same size as the object |
| Between F and 2F | Real, inverted, larger than the object |
| Closer than F | Virtual, upright, larger (a magnifying glass) |
An object 1.5 cm tall forms an image 4.5 cm tall through a converging lens. Find the magnification.
The magnifying glass image, formed when the object is closer than the focal length, is virtual, upright and enlarged, and cannot be caught on a screen. Only a real image, formed when the object is beyond the focal length, is inverted and can be projected.
Unlocks once the four checks above are done. Worth more XP, written in the style of Paper 2.
An object is placed beyond 2F in front of a converging lens. The image is...
An object 2.0 cm tall produces an image 8.0 cm tall. The magnification is...
Looking at small print through a magnifying glass held close to the page, you see an image that is...
The converging lens is mapped. Keep the chain going.