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?

Rad

io w

aves

.

Vis

ible

light w

aves

.

Ultr

avio

let w

ave.

Gam

ma

rays

.

5

15

20

A. Radio waves.

B. Visible light waves.

C. Ultraviolet wave.

D. Gamma rays.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

21 22 23

17

An electromagnetic wave is what type of wave?

Longi

tudin

al w

ave.

Surfa

ce w

ave.

Tra

nsver

se w

ave.

Mec

hanic

al w

ave.

4

1

16

1

A. Longitudinal wave.

B. Surface wave.

C. Transverse wave.

D. Mechanical wave.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

21 22 23 24

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. B. C. D.

4

1

99A. Concave.

B. Convex.

C. Both concave and convex.

D. Neither concave nor convex.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

21 22 23 24

22

Which type of lens is used to correct nearsighted vision?

A. B. C. D.

21

011

A. Concave.

B. Convex.

C. Both concave and convex.

D. Neither concave nor convex.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

21 22 23 24

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!!!!!!!!!!!!!!!!!!!!