1 Electromagnetic Spectrum Chapter 17 & 18

2 Electromagnetic Waves Electromagnetic waves are transverse waves that have some electrical properties and some magnetic properties. An electromagnetic wave consists of changing electric and magnetic fields.

3 Electromagnetic Radiation The energy that is transferred by electromagnetic waves is called electromagnetic radiation. All electromagnetic waves travel at the same speed: 300,000, 000 m/s.

4 Wave or Particles? Light has many of the properties of waves. But light can also act as though it is a stream of particles. When light passes through a polarized filter, it has the properties of a wave.

5 Wave or Particles? When a beam of light shines on some substances, it causes tiny particles called electrons to move (photoelectric effect). Light is a stream of tiny packets or particles known as photons.

6 Characteristics of Electromagnetic Waves All electromagnetic waves travel at the same speed, but they have different wavelengths and different frequencies. Remember: Speed=wavelength x frequency

7 Different Wavelengths of the Electromagnetic Spectrum In order of decreasing wavelength: Radio Infrared Visible light Ultraviolet X ray Gamma ray

8 What happens to light when is strikes a surface? Light can be reflected, absorbed or transmitted when it strikes a surface. You can not see through objects that are opaque. A transparent material transmits light. Translucent materials scatter light as it passes through.

9 Types of Reflection Regular reflection occurs when the light waves hit a smooth surface. Diffuse reflection occurs when the light waves hit a rough surface and the light waves are scattered.

10 Types of Mirrors Concave mirrors are mirrors that curve inward. These type of mirrors can produce virtual & real images. Convex mirrors are mirrors that bulge outward. These type of mirrors can produce virtual images. Plane mirrors produce virtual images.

11 Type of Images Real images are inverted images formed where rays of light meet. Virtual images are upright images formed where rays of light appear to meet or come from.

12 Refraction Refraction happens when light waves changes speed as it goes through different mediums. As light waves change speed the waves bend.

13 Effects of Refraction Refraction makes objects appear to be in different positions. Refractions in the atmosphere creates mirages.

14 Rainbows Raindrops act like tiny prisms, refracting and reflecting the light and separating the colors. ROY G BIV –Red –Orange –Yellow –Green –Blue –Indigo –Violet

15 Mirage A mirage is an image of a distant objects caused by refraction of light.

16 Which form of electromagnetic wave has the shortest wavelength, but the greatest energy? A.Radio waves. B.Visible light waves. C.Ultraviolet wave. D.Gamma rays.

17 An electromagnetic wave is what type of wave? A.Longitudinal wave. B.Surface wave. C.Transverse wave. D.Mechanical wave.

18 Lenses A lens is a curved piece of glass. Lenses can magnify images. Magnification is any change in the size of an image compared with the size of the object.

19 Type of Lenses Converging lens bends the light inward that produces a virtual or real image. (convex lens) Diverging lens bends the light outward and can produce only a virtual image. (concave lens)

20 Correct Vision Nearsightedness is when you only see things clearly that are close. –Eyeball is too long. –Corrected by concave lens. Farsightedness is when you only see things clearly that are far. –Eyeball is too short. –Corrected by convex lens.

21 Which type of lens converge light to a focal point? A.Concave. B.Convex. C.Both concave and convex. D.Neither concave nor convex.

22 Which type of lens is used to correct nearsighted vision? A.Concave. B.Convex. C.Both concave and convex. D.Neither concave nor convex.

23 Other Uses of Light & Lenses Telescopes Microscopes Cameras Lasers –CD’s –DVD’s Optic Fibers –Communications –Surgery

24 Colors The color we see is the light being reflected from the object. Additive primary colors are red, green & blue. Subtractive primary colors are yellow, cyan and magenta.

25 Colors and Pigments If all colors are reflected, you see white light. If all colors are absorbed, you see black.

26 Review Questions What type of wave is light? Transverse What is the longest wavelength of the electromagnetic spectrum? Radio Which type of electromagnetic waves have the most energy? gamma

27 Review Questions What are the three primary colors? Red, blue, green What is the speed of light? 300,000 km/s Which type of lens converges light to a focal point? Convex

28 Review Questions Which type of mirror produces either a virtual or real image? Concave Which type of image is up-side-down? Real What do we call objects that only reflect light? opaque

29 Review Questions What do we call objects that transmit light? Transparent What do we call objects that don’t transmit light clearly? Translucent Which type of lens corrects nearsightedness? concave

30 Review Questions Which type of lens corrects farsightedness? Convex What happens when light is bent as it changes medium? Refraction What happens when light reflects off of an surface? Reflection

31 Review Questions The End Study!!!!!!!!!!!!!!!!!!!!