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Light Chapter 18.

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Presentation on theme: "Light Chapter 18."— Presentation transcript:

1 Light Chapter 18

2 Section 1 - Light and Color
When light strikes an object, the light ca be reflected, transmitted, or absorbed. Transparent - a material that transmits most of the light that strikes it Translucent - a material that scatters light as it passes through Opaque - a material that reflects or absorbs all of the light Chapter 18

3 Light and Color The color of an object depends on the object’s material and the color of the light striking the object. Every object absorbs some wavelengths of light and reflects others. The color of an opaque object is the color of the light it reflects. The color of a transparent or translucent object is the color of the light it transmits. Chapter 18

4 Light and Color Primary colors – three colors that can combine to make any other color red, green , blue Secondary colors – produced when two primary colors combine in equal amounts magenta, yellow, and cyan White light – produced when the three primary colors are combined in equal amounts. Chapter 18

5 Light and Color Complementary colors – any two colors that combine to form white light. Pigments – colored substances that are used to color other materials As pigments are added together, fewer colors of light are reflected and more absorbed. Chapter 18

6 Section 2 - Reflection and Mirrors
light rays represent light waves as straight lines The two ways in which a surface can reflect light are regular reflection and diffuse reflection pg.618 Regular – when parallel rays of light hit a smooth surface Diffuse - when parallel rays of light hit a bumpy or uneven surface Chapter 18

7 Reflection and Mirrors Plane Mirror
Plane mirror – a flat sheet of glass that has a smooth, silver-colored coating on one side image - copy of an object formed by reflected or refracted rays of light produces a virtual image right side up the same size as the object being reflected behind the mirror Chapter 18

8 Reflection and Mirrors Concave Mirrors
Surface curves inward like a bowl used for make-up mirrors Optical Axis – an imaginary line that divides a mirror in half (equator) Focal Point – the point at which rays parallel to the optical axis meet. Ray Diagram Forms either a virtual image or real image (pg. 621) Chapter 18

9 Reflection and Mirrors Concave Mirrors
Real Image – forms when rays actually meet Upside down Larger or smaller than the object Image Real - farther than the focal point In front and upside down Chapter 18

10 Reflection and Mirrors Concave Mirrors
Image (Cont’d) Virtual - Closer than the focal point Behind and upright At the focal point - no image is formed Forms parallel light rays Headlights Chapter 18

11 Reflection and Mirrors Convex Mirrors
Surface curves outward. Forms a smaller virtual image (pg. 622) used for security or blind spots on roads Chapter 18

12 Section 3 - Refraction and Lenses
When light rays enter a medium at an angle, the change in speed causes the rays to bend, or change direction Two images in fish tank index of refraction - a measure of how much a ray of light bends when it enters that material (pg. 624) Chapter 18

13 Refraction and Lenses Prisms and Rainbows
Longer wavelengths (red) refracted less Shorter wavelengths (violet) refracted more Separates the colors of white light mirage - an image of a distant object caused by refraction of light (by hot air) Lens – a curved piece of glass or other transparent material that is used to refract light Chapter 18

14 Convex lens Thicker in the center than at the edges
parallel light rays are bent towards the center of the lens (pg. 626) forms virtual or real image dependent upon position relative to the focal point Chapter 18

15 Concave lenses Thicker at the edges than in the center
parallel light rays are bent away from the center of the lens (pg. 627) forms virtual image (again because rays can never meet) Chapter 18

16 Section 4 - Seeing Light You see an object when a process occurs that involves both your eyes and your brain. Chapter 18

17 Section 4 - Seeing Light Eye picture pg. 631 cornea - pupil - iris -
lens - retina - optic nerve - Chapter 18

18 Seeing Light nearsighted - can see close objects clearly
eyeball too long. corrected with concave lens Farsighted - can see far away objects clearly eyeball too short. Corrected with convex lens Chapter 18

19 Section 5 - Using Light Optical Instruments
Telescope uses lenses or mirrors to collect and focus light from distant objects. Images are upside-down Refracting telescope Objective Eyepiece Reflecting Chapter 18

20 Using Light Optical Instruments
(Light) Microscope – uses a combination of lenses to produce and magnify an image Camera – use a lens to focus light to form a real, upside-down image on the back of the (film) camera Chapter 18

21 Using Light Lasers Light amplification by stimulated emission of radiation Laser light consists of light waves that all have the same wavelength, or color. The waves are coherent, or in step. Uses Compact discs Holography Surgery Chapter 18

22 Using Light Optical Fibers – long, thin strands of glass or plastic that can carry light for long distances without allowing the light to escape. Total internal reflection – complete reflection of light by the inside surface of the medium Medicine Communication Chapter 18

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