1. Examples of Total Internal Reflection
Do Now
Total internal reflection sheet

2. Lenses

3. Lenses
You have two lenses on your bench, one that is thick in the middle (converging) and one that is thin in the middle (diverging). Try looking through them.

4. Converging and diverging lenses
WHY?

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

6. 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.

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

8. 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.

9. 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

10. 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

11. Drawing ray diagrams

12. Drawing ray diagrams

13. Drawing ray diagrams

14. Drawing ray diagrams

15. 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.

16. Drawing ray diagrams

17. Do Now – 1. Stick in ray diagrams. 2. Draw the following table 3
Do Now – 1. Stick in ray diagrams. 2.Draw the following table 3. Fill in
Object at
Image at
Size
Orientation
Nature
Use
>2F
Image on a film close up 2F
Photocopier
Between 2F and F
Projector F
Spot light
<F
Magnifying glass

18. Now construct the following 5 diagrams
An object at greater than 2F
an object at 2F
an object less than 2F
an object at F
an object at less than F

19. Image on a film (at infinity)
Object at
Image at
Size
Orientation
Nature
Use
Infinity F
Diminished
Inverted
Real
Image on a film (at infinity)
>2F
Between F and 2F
Image on a film
(close up) 2F
Same size
Photocopier
Between 2F and F
Magnified
Projector
Spot light
<F
<F (on same side)
Upright
Virtual
Magnifying glass

22. Virtual image

23. Let’s try it! – Investigating images practical on Wednesday

24. Diffraction

25. Diffraction definition
Waves spread as they pass an obstacle or through an opening

26. Diffraction –diagrams are important
Diffraction is most when the opening or obstacle is similar in size to the wavelength of the wave There is less diffraction when the opening is larger than the wavelength

27. Diffraction
Diffraction is most when the opening or obstacle is similar in size to the wavelength of the wave

28.                                                                 
                                                                
                                                                
                                                                
Diffraction
That’s why we can hear people around a wall but not see them!

29.                                                                 
                                                                
                                                                
                                                                
Do now stick in all you loose sheet and read the practical questions – this will be assessment
you will need for the exam.
pen, pencil
ruler, rubber and protractor
calculator

30. Learning today How images are formed
Using the formulae for magnification and focal length – you are given these in the question

31. Investigating images practical

32. Let’s try some questions