Chapter 5: Mirrors and Lenses. 5.1 Ray Model of Light

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1 Chapter 5: Mirrors and Lenses 5.1 Ray Model of Light

2 Ray Model of Light Another model for light is that it is made up of 3ny par3cles called photons Photons travel in perfect, straight lines away from a light source This model helps us to understand and predict light s behaviour, par3cularly with mirrors and lenses.

3 Light and Ma>er Transparent objects that transmit light waves. Transluscent objects that transmit some light waves. Objects are not seen clearly through them. Opaque objects that absorb or reflect light waves.

4 Shadows Ray diagrams can be used to explain shadows Light from a light source is blocked by an object, cas3ng a shadow behind the object The size of the shadow depends on the distance from the light source

5 When light bounces off an object, we say it reflects The incoming ray is called the incident ray. The outgoing ray, that bounces off the object, is called the reflected ray ReflecGon

6 ReflecGon A dofed line can be drawn that is perpendicular to the surface of the object; this is called the normal. The angle between the incident ray to the normal is the same as the angle of the reflected to the normal.

7 RefracGon When light moves from air into glass, it slows down and changes direcgon because glass is denser than air. The angle of refracgon is the angle between a ray of light emerging from the boundary between two materials and the normal.

$RefracGon When light passes into more dense material, it bends towards the normal (and slows$

8 RefracGon When light passes into more dense material, it bends towards the normal (and slows down) When light passes into less dense material, it bends away from the normal (and speeds up)

$Refrac3on causes op3cal$ water.

9 Refrac3on causes op3cal illusions of objects under water. They oken appear to be closer to the surface than they really are.

$Mirages are formed by the refrac3on of light as it passes from less dense hot air to more dense cool air.$

10 Mirages are formed by the refrac3on of light as it passes from less dense hot air to more dense cool air. On a hot day, air near the ground surface gets very hot compared to the air above. Light traveling from the sky gets bent as it passes through the hot air, which then appears to eye to be pools of water

12 5.2 Mirrors

13 ReflecGon Mirrors and highly polished objects reflect light. Law of ReflecGon angle of incidence = angle of reflec3on

14 Images in a Mirror

15 Plane Mirrors image appears behind the plane mirror erect and same size image is inverted sideways but not ver3cally

16 curve inward Concave Mirrors reflect light like a plane mirror, but reflected light rays meet at a single point called a focal point these light rays that come together are called converging rays

17 Images formed in Concave Mirrors distant objects appear to be smaller and upside down ( inverted ) As you approach the focal point of the mirror, the object gets bigger, but is s3ll inverted

18 Images formed in Concave Mirrors If an object is between the focal point and the mirror, the image is larger and upright.

20 Uses for Concave Mirrors lights placed at the focal point will reflect out of the mirror in straight lines used in headlights and spotlights make- up and shaving mirrors are concave so that your image is enlarged (making it easier to see)

21 Convex Mirrors curve outward reflect parallel light as if it were coming from a focal point behind the mirror since the light rays spread apart aker hisng the mirror, they are called diverging rays.

22 Images in Convex Mirrors objects appear smaller than they really are a wider view be seen than in a plane mirror of the same size

23 Uses for Convex Mirrors security mirrors in stores side- view mirrors in cars

24 5.3 Lenses

25 Lenses Light bends as it passes through glass and then bends again as it passes back into air A lens is a curved piece of transparent material that bends light in a controlled way Lenses can cause light rays to converge or diverge as they pass through them

26 Concave Lenses Thinner in the middle than at the edge Light rays diverge or spread out as they pass through the lens Image formed is upright and smaller than the actual object

27 Uses for Concave Lenses some eyeglasses (near- sightedness) some telescopes spy glasses in doors

28 Convex Lenses Thicker in the middle than at the edge Light rays converge or come together as they pass through the lens Image formed depends on the posigon of the object with respect to the mirror

29 Focal Length in Convex Lenses light rays converge at a point called the focal point The distance from the focal point to the centre of the lens is the focal length

30 An object far away from the lens appears inverted (upside down) and smaller

31 An object close to the lens is upright and magnified

32 Uses for Convex Lenses Magnifying glass Overhead projector Microscopes Eyeglasses (long- sighted)

Chapter 5 Mirror and Lenses

Chapter 5 Mirror and Lenses Name: 5.1 Ray Model of Light Another model for light is that it is made up of tiny particles called. Photons travel in perfect, lines from a light source This model helps us