1. Light Waves Physics 1 H Created by Stephanie Ingle

2. Light Light is a transverse wave. Light waves are electromagnetic waves--which means that they do NOT need a medium to travel. Light waves behave like other waves and have the same characteristics such as amplitude, frequency, and wavelength.

3. Characteristics of Light Intensity (brightness) -- represented by amplitude Color -- determined by frequency Wave speed - depends on the medium Light waves as well as ALL Electromagnetic waves travel with a speed of 3.0 x 10 8 m/s in a vacuum.

4. Characteristics of Electromagnetic Waves Made up of 2 components –electric field & magnetic field The electric and magnetic fields are perpendicular to each other. A changing electric field will create a magnetic field and a changing magnetic field will create an electric field; therefore the wave propagates itself through space without need of a medium.

5. Electromagnetic Waves Radio Microwaves Infrared Visible Light Ultraviolet X-rays Gamma Rays All of these follow the same rules as Light and travel at the same speed. They are listed in order of increasing frequency and energy and decreasing wavelength Light is the visible part of the spectrum

6. Luminous vs Illuminated Luminous –a body that emits light –has luminous flux Illuminated –a body that reflects light –no luminous flux –does not emit light of its own

7. Luminous Flux (P) Luminous flux is the rate at which light energy is emitted from the source. Equivalent to Power Measured in lumens (lm)

8. Luminous Intensity (I) The amount of light (luminous flux) that falls on one square meter at a distance of 1 meter from the source. Equivalent to Intensity at r = 1 m Measured in candelas (cd)

9. Illuminance (E) Amount of light that falls on a surface Intensity of light at any given distance from source measured in lux lux = lumen/m 2 bulb r

10. Reflection & Mirrors

11. Law of Reflection Angles are always measured from the normal, never the surface Angle of incidence equal angle of reflection  i =  r rr ii incident ray reflected ray normal Mirror surface

12. Types of Reflection Regular Reflection –When parallel rays of light fall on a smooth surface they are reflected parallel from the surface. Diffuse Reflection –When parallel rays of light fall on a textured surface they are reflected in many different directions. They are diffused.

13. Concave Mirrors Reflective surface, like inside of a spoon, forms a “cave” Parallel rays of light from a far object will converge at the focal point. Concave Mirrors also called “converging mirrors” Focal point is half the distance from the center of curvature (C) to the mirror f = R/2, where R is radius of curvature

14. Convex Mirrors Reflective surface, like back of a spoon or outside of curve Parallel rays of light from a far object will diverge as if they originated at the focal point. Convex Mirrors also called “diverging mirrors” Focal point is half the distance from the center of curvature (C) to the mirror f = R/2, where R is radius of curvature

15. Calculations f = focal length d o = object distance d i = image distance h i = image height h o = object height M = magnification

16. Interpreting Calculations Focal length (f) concave or converging, then f is + convex or diverging, then f is - Image distance (d i ) d i is +, then image is real d i is -, then image is virtual Magnification (M) M = +, image is erect and virtual M = -, image is inverted and real

17. C f Ray Diagram Concave Mirror (object beyond C) Draw 2 rays from tip of object: 1) parallel, then through f 2) through f, then parallel The image is formed where the reflected rays intersect. object image Image is real, inverted, & reduced

18. C f object image Ray Diagram Concave Mirror (object at C) Draw 2 rays from tip of object: 1) parallel, then through f 2) through f, then parallel Image is real, inverted, & same size

19. Ray Diagram Concave Mirror (object between f & C) f C object image Image is real, inverted, & magnified Draw 2 rays from tip of object: 1) parallel, then through f 2) through f, then parallel

20. Ray Diagram Concave Mirror (object inside f) f C object image Draw 2 rays from tip of object: 1)parallel, then through f 2)as if it came from the focal point and then parallel 3)extend the reflected rays behind mirror to locate image Image is virtual, erect, & magnified

21. Cf Ray Diagram Convex Mirror object image Draw 2 rays from tip of object: 1)parallel, then reflect as if ray came from focus 2)toward the focal point, then parallel 3)extend the reflected rays behind the mirror to locate the image Image is virtual, erect, & reduced