Write the names of the seven electromagnetic waves in the order of frequency (low to high)

1. Write the names of the seven electromagnetic waves in the order of frequency (low to high) The frequency of an electromagnetic wave is measured to be 1.6 x 1018 Hz. What type of electromagnetic wave would it be? The wavelength of microwave radiation produced by a microwave oven is 12.2 cm. Calculate the corresponding frequency.

2. ATOYOT

3. How do we “see” things?

9. Plane Mirrors Eye sees image back here Image is virtual and laterally inverted Light from object reflects into eye

11. Convex (diverging) Mirrors

17. Concave (converging) Mirrors

26. Plane Mirrors Eye sees image back here Image is virtual and laterally inverted Light from object reflects into eye

27. Concave Mirrors • Concave (or converging) mirrors focus light at the focal point. F

28. Convex Mirrors • Convex mirrors have a focal point behind the mirror. • Convex (or diverging) mirrors spread the light rays apart so that they appear to have come from the focal point F

31. Convex (diverging) mirrors A convex mirror always produces virtual images which are always upright and smaller than the object. The image is formed behind the mirror, between the principal focus and the mirror. Concave (converging) mirrors The image will be real, invertedif the object is located behind the principal focus. The image will be virtual, upright and enlargedifthe object is located between the mirror and the principal focus.

32. r pa P F C f P = pole , pa = principal axis C = centre of curvature r = radius of curvature F = Focal point or focus f = focal length f = r / 2

33. Ray Diagrams • Rule 1: An incident ray parallel to the pa is reflected back through the focal point. F

34. Ray Diagrams • Rule 2: An incident ray that passes through the focal point on the way to the mirror is reflected back parallel to the pa. F

35. Ray Diagrams • Rule 3: An incident ray headed towards the pole reflects back at an equal angle P F

36. How to draw ray diagrams Step 1. mirror → pole → mirror line → Principal axis → principal focus (F) → object (arrow) Step 2. Draw a ray travelling horizontally from the top of the object towards the mirror Step 3. If Concave = Focus If Convex = Pole

37. Concave (converging) Mirror When the object is located behind the principal focus.

38. Concave (converging) Mirror When the object is located between the mirror and the principal focus.

39. Convex (diverging) mirrors

40. Draw these ray diagrams An object is standing in front of a concave mirror, closely behind its focus. An object is standing in front of a concave mirror, far behind its focus. An object is standing between a concave mirror and its focus. An object is standing in front of a convex mirror.

41. Mirror Formulae ONE • Descartes’ Formula: • Or: • m=magnification factor • h=height of image or object • d=distance from mirror to image or object • Distances behind the mirror are negative • hi is negative if the image is virtual

42. Using Descartes’ Formula – EXAMPLES a) Find the position of the image located 40m in front of a concave mirror of radius of curvature 64m. b) An object 7m high is placed 15m from a convex mirror of radius 45m. Find the position AND the height of the image.

43. Mirror Formulae TWO • Newton’s Formula: • Or: • S=distance from focal point to image or object • All distances are positive but care must be taken when calculating Sior So. • It is usually necessary to sketch a ray diagram to check.

44. Using Newton’s Formula – EXAMPLES a) An object 7m high is placed 15m from a convex mirror of radius 45m. Find the position AND the height of the image. b) An object 6m high is placed 30m in front of a convex mirror of focal length 40m. Find the position, nature and size of the image formed.

45. Finish these by this Thursday Homework Booklet Worksheet TWO NCEA 2004 & 2005 NCEA 2008 Activity 5B