1. Do now!
Can you write in your planners that you MUST bring sunglasses to next lesson! (Monday 3rd October)

2. Don’t forget!
“Mug-trick” homework due on Monday

3. Refraction Beam of light Glass block
Light going from air to glass bends towards the normal
Glass block
Light going from glass to air bends away from the normal

4. Converging lenses

5. Follow Mr Porter
You need your lens, a ruler, a pencil/pen and your book.

6. Finding the focal length - a quick practical
Use the “distant light” method to show the students how to find the focal length. Give them a number of unmarked lenses that they have to find the focal length to.

7. Principal axis
The straight line that goes through the centre of the lens at right angles to the lens surface

8. Principal focus
Rays parallel to the principal axis, after being refracted by the lens, will all pass through a point on the principal axis called the principal focus.

9. Focal length
The distance from the principal focus to the centre of the lens (denoted by the symbol f)

10. Let’s try it! – Investigating images practical

11. Real and virtual images
A real image is where the rays actually pass through the image and it can be projected and seen on a screen

12. Real and virtual images
A virtual image is where no rays of light pass through, only their mathematical extensions. It cannot be displayed on a screen

13. Let’s construct some ray diagrams to find out!
Why?
Let’s construct some ray diagrams to find out!

14. Can you stick the sheet in please?
Do now!!
Can you stick the sheet in please?

15. Investigating images practical

16. Can you read Mr Porter’s comments in your book please.
Do now!
Can you read Mr Porter’s comments in your book please.

17. Drawing ray diagrams

18. Drawing ray diagrams

19. Drawing ray diagrams

20. Drawing ray diagrams

21. Drawing ray diagrams
You can check by drawing a ray backwards from the object parallel to the axis which has passed through the first principal focus.

22. Drawing ray diagrams

23. Let’s construct some ray diagrams!

26. Virtual image

28. Let’s try some questions

29. Astronomical telescope
This is the 24 inch reflecting telescope at the Lowell Observatory in Flagstaff, Arizona, which was used to discover Pluto. Nearly all astronomical telescopes use mirrors rather than lenses, but we will learn how a telescope with lenses works.

30. Telescope – Ray diagram
Angular magnification = fo/fe

31. Let’s make a telescope!
Proud man

32. Don’t forget!
Homework