Physics 1 H Created by Ingle Light Waves Physics 1 H Created by Ingle Stephanie

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.

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 108 m/s in a vacuum.

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.

Other Electromagnetic Waves Radio Microwaves Infrared Ultraviolet X-rays Gamma Rays Radar All of these follow the same rules as Light and travel at the same speed. Light is simply a way of referring to the visible portion of the electromagnetic spectrum.

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

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

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) I = P/4 or cd = lm/4

Illuminance (E) E = P/(4r2) Amount of light that falls on a surface Intensity of light at any given distance from source measured in lux lux = lumen/m2 r bulb E = P/(4r2)

Reflection & Mirrors

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

Types of Reflection Regular Reflection Diffuse 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.

Concave Mirrors Reflective surface to the inside of curve, 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

Convex Mirrors Reflective surface to the outside of curve (back of spoon) 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

Calculations f = focal length do = object distance di = image distance hi = image height ho = object height M = magnification

Interpreting Calculations Focal length (f) converging, then f = + diverging, then f = - Image distance (di) di=+ , then image is real di= -, then image is virtual Magnification (M) M = +, image is erect M = - , image is inverted

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

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

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

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

Ray Diagram Convex Mirror Draw 2 rays from tip of object: 1) parallel, then reflect as if ray came from f, 2) toward focal point, then parallel, extend reflected ray behind mirror image object f C Image is virtual, erect, & reduced