Images (CIE IGCSE Physics: Co-ordinated Sciences (Double Award))

• An image can be described using the following characteristics which compare it to the object:
  • Enlarged/same size/diminished
  • Upright/inverted
• An image viewed through a magnifying glass is:
  • Enlarged, bigger than the object
  • Upright, has the same orientation as the object

An image viewed through a magnifying glass

An image viewed through a magnifying glass is enlarged and upright compared to the object

• An image viewed through an eye, a camera, or a glasses lens is:
  • Diminished, smaller than the object
  • Inverted, upside down compared to the object

An image viewed by the eye

An image viewed by the eye is diminished and inverted compared to the object

Constructing converging ray diagrams

• The three main rules for constructing ray diagrams are as follows:

1. Rays passing through the principal axis will pass through the optical centre of the lens undeviated

 

 

2. Rays that are parallel to the principal axis will be refracted and pass through the focal point f

 

 

3. Rays passing through the focal point f will emerge parallel to the principal axis

 

Drawing converging ray diagrams of real images

• For an object placed at a distance greater than 2 focal lengths...

A converging lens ray diagram for an object placed further than 2f

• The image that forms will have the following properties:

The image forms...	between f and 2f
The nature of the image is...	real
The orientation of the image is...	inverted
The size of the image is...	diminished

 

 

• For an object placed at a distance equal to 2 focal lengths...

A converging lens ray diagram for an object placed at 2f

• The image that forms will have the following properties:

The image forms...	at 2f
The nature of the image is...	real
The orientation of the image is...	inverted
The size of the image is...	the same

 

 

• For an object placed at a distance between 1 and 2 focal lengths

A converging lens ray diagram for an object placed between f and 2f

• The image that forms will have the following properties:

The image forms...	beyond 2f
The nature of the image is...	real
The orientation of the image is...	inverted
The size of the image is...	magnified