Geometrical Optics Introduction

Geometrical Optics Introduction

1. GEOMETRIC OPTICS INTRODUCTION RABIA AMMER OPTOMETRIST & ORTHOPTIST

2. LEARNING OUTCOMES Optics Light Types of Optics Geometrical Optics Mirror & Lenses Ray Tracing

3. WHAT IS OPTICS…???

4. OPTICS Optics is the science of LIGHT O ne of the most important fields of PHYSICS .

5. Optics involves the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it.  Optics usually describes the behavior of visible, ultraviolet, and infrared light.

6. WHAT IS LIGHT…???

7. LIGHT It's a type of energy. Light  is electromagnetic radiation within a certain portion of the electromagnetic spectrum. The word usually refers to  visible light , which is visible to the human eye and is responsible for the sense of sight.  Visible light is usually defined as having wavelengths in the range of 400–700 nanometers (nm), B etween the infrared (with longer wavelengths) and the ultraviolet (with shorter wavelengths).

8. OPTICAL REDIATIONS Lies between X- rays and microwaves. Wave length 200nm – 10,000nm. Divided into 7 bands UV C UV B UV A Visible Light IR A IR B IR C

9. LIGHT PROPERTIES How does light travel? FAST and STRAIGHT. How FAST? 300,000 kilometers per second How STRAIGHT? Perfectly straight, until something bends it. The straight paths of light are called LIGHT RAYS.

10. Controlling Light There are THREE basic ways to control light Block it ... with something (this makes a shadow) Reflect it (change its path with a mirror) Bend it (converge or diverge with a lens)

11. TYPES OF OPTICS…

12. TYPES OF OPTICS Optics Is Divided Into Three Main Branches: Physical Optics Geometrical Optics Quantum Optics

13. Physical Optics: W ave O ptics, Light is considered to be an electromagnetic wave. Geometrical Optics: Ray Optics, Light is considered to travel in straight lines . Quantum Optics: Photon Optics, Light is considered to have particles nature.

14. GEOMETRICAL OPTICS Geometrical optics , or  ray optics , describes the propagation of light in terms of "rays" which travel in straight lines, and whose paths are governed by the laws of reflection and refraction at interfaces between different media .  These laws can be summarized as follows: When a ray of light hits the boundary between two transparent materials, it is divided into a reflected and a refracted ray . It deals with the formation of images by u sing optical devices such as mirrors, lenses and prisms.

15. A ray of light is an extremely narrow beam of light.

16. All visible objects emit or reflect light rays in all directions.

17. Our eyes detect light rays.

18. We think we see objects. We really see images.

19. When light rays go straight into our eyes, we see an image in the same spot as the object. object & image

20. How do we see images in mirrors?

21. object image Light from the object reflects off the mirror and converges to form an image. How do we see images in mirrors?

22. SIGHT LINES object image We perceive all light rays as if they come straight from an object. The imaginary light rays that we think we see are called sight lines .

23. IMAGE TYPES object image Real images are formed by light rays . Virtual images are formed by sight lines . mirror object & image window

24. SPHERICAL SURFACES (CONCAVE & CONVEX)

25. CONCAVE & CONVEX (JUST A PART OF A SPHERE) C : the center point of the sphere r : radius of curvature (just the radius of the sphere) F : the focal point of the mirror or lens (halfway between C and the sphere) f : the focal distance, f = r /2 r f • C • F

26. TERMINOLOGIES The Center Of Curvature , C, is the center of the sphere, of which the mirror is a section. The Principal Axis is the line that passes through the center of curvature and the center of the mirror. The principal axis is perpendicular to the surface of the mirror at A. CA is the Radius Of The Sphere , or the radius of curvature of the mirror, R . The point at which the rays converge is called the focal point. Halfway between C and A is the Focal Point of the mirror, F. This is the point where rays parallel to the principal axis will converge when reflected off the mirror . The length of FA is the Focal Length , f . The focal length is half of the radius of the sphere

27. REAL VS. VIRTUAL IMAGES Real images When light rays actually converge and pass through the mirror. Located in front of the mirror forming them. Can be projected onto a piece of paper or a screen. Virtual images Occur where light rays only appear to have originated. Rays appear to be coming from a point behind the mirror. Can’t be projected on paper, screens, or film since the light rays do not really converge there.

28. MIRRORS A smooth and well polished srfacethat reflect regularly most of light falling on it. Types: Plane Mirror: Plane sheet of glass one surface is silvered other surface is polished. Spherical Mirror: Part of a hollow sphere one surface is silvered other surface is polished.

29. CONCAVE AND CONVEX MIRRORS light rays light rays Concave mirrors reflect light from their inner surface Convex mirrors reflect light from their outer surface

30. LENSES Lenses are made of transparent materials, like glass or plastic Refract the incident light H ave an index of refraction greater than that of air. Each of a lens has two faces either part of a sphere or cylinder and can be convex or concave (or one face may be flat).

31. CONCAVE AND CONVEX LENSES light rays light rays Concave Lenses refract light from their inner surface Convex Lenses refract light from their outer surface

32. RAY TRACING

33. PLANE (FLAT) MIRRORS object image Images are virtual (formed by sight lines ) and upright d o d i h i h o

34. optical axis CONCAVE MIRROR • F The first ray comes in parallel to the optical axis and reflects through the focal point .

35. optical axis CONCAVE MIRROR • F The second ray comes through the focal point and reflects parallel to the optical axis. A real image forms where the light rays converge.

36. CONVEX MIRROR optical axis • F The first ray comes in parallel to the optical axis and reflects through the focal point .

37. CONVEX MIRROR optical axis • F The second ray comes through the focal point and reflects parallel to the optical axis. The light rays don’t converge, but the sight lines do.

38. LENSES Light rays are always refracted (bent) towards the thickest part of the lens. convex lens concave lens light from far away object

39. CONCAVE LENS optical axis • F The first ray comes in parallel to the optical axis and refracts from the focal point .

40. CONCAVE LENS optical axis • F The second ray goes straight through the center of the lens. The light rays don’t converge, but the sight lines do.

41. CONCAVE LENS optical axis • F A virtual image forms where the sight lines conver ge.

42. CONVEX LENS • F The first ray comes in parallel to the optical axis and refracts through the focal point . optical axis

43. Convex Lens optical axis • F The second ray goes straight through the center of the lens. The light rays don’t converge, but the sight lines do.

44. CONVEX LENS optical axis • F A virtual image forms where the sight lines converge .

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