1. Peer mark the homework

2. Peer mark the homework

3. Learning Goals
By the end of this lesson you should be able to…
Draw ray diagrams to identify the size and position of the image produced
Describe the images formed by convex and concave lenses from the ray diagram
Explain the effect of moving the object towards or away from the lens
Apply the equation for magnification of a lens to the ray diagram produced.

4. Diverging or Converging Lens

5. Drawing Ray Diagrams
Diagrams should be drawn to scale
Draw object as arrow pointing upwards
Draw convex lens as
Draw concave lens as
Construct diagram using two rays

8. Drawing Ray Diagrams 6 Steps... Draw your lens and a principle axis.
Mark your Focal point (F) on both sides of the lens using information given.
Draw your image as an arrow up from the principle axis.
Draw one ray going through the centre of the lens, undeflected.
Draw a second ray parallel to the principle axis, deflecting through the Focus once it has passed through the lens.
Look for where the 2 rays meet!

9. object F F
Focal Length = 9cm

10. Drawing Ray Diagrams 6 Steps... Draw your lens and a principle axis.
Mark your Focal point (F) on both sides of the lens using information given.
Draw your image as an arrow up from the principle axis.
Draw one ray going through the centre of the lens, undeflected.
Draw a second ray parallel to the principle axis, deflecting through the Focus once it has passed through the lens.
Look for where the 2 rays meet!

11. How can we describe the image formed?
object F
image F
How can we describe the image formed?

12. How do we describe our image?
Magnified, same size or reduced
Upright or inverted
Real or virtual

13. Focal length of lens = 4cm Object height = 2cm
Drawing Ray Diagrams
Focal length of lens = 4cm
Object height = 2cm
Draw accurate ray diagrams on graph paper to show & describe the image formed in these situations.
Object distance (from lens) = 7cm
Object distance (from lens) = 2cm

14. This image is magnified, erect (upright) and virtual
eye
This image is magnified, erect (upright) and virtual

15. Drawing ray diagrams – concave lensF
Principal Axis
Still two rays are needed, one parallel and one through the centre of lens. Image is virtual and diminished.

16. The magnification of an image is given by:
Magnification = Image size
Object size

17. Work through worksheet
Can complete this worksheet (directly on the sheet (double sided A4) or…

18. Work through worksheet
Complete this worksheet – onto graph paper.

19. Focussing a Camera

20. Complete worksheet
Complete worksheet – understanding lenses. Beware, there is a question about stability thrown in to get you thinking back to Y9… look it up if you’re not sure.

21. Homework
Revise topic to date ready for a quick progress test at the start of the next lesson.
Prepare a topic summary sheet, revision cards, mind map, questions to test yourself & bring them to the next lesson.
DON’T forget you MUST learn v = f λ equation you need to be able to recall this one.

22. Real or Virtual? Mirror Camera Projector Binoculars Magnifying glass
Eye
Microscope
Remember with a virtual image the rays will never really converge but it will appear that the image you are seeing converges behind the lens.