1. Characteristics of Light
Chapter 14 Section 1

2. Light
Most people think of light as only being admitted from a light bulb or the sun in the form of white light.
White light is the combination of multiple colors of light combined into one.

3. Visible Light Spectrum
Red
Orange
Yellow
Green
Blue
Indigo
Violet

4. Prism
A Prism can be used to separate white light into the colors of the visible light spectrum.

5. Particle or wave?
Light can be described as a particle, as a wave, and even as a combination of the two.
Wave model is best suited for introductory discussion of light.

6. Light Spectrum
The spectrum of light is not confined to just visible light.
There are many variations of light:
Radio waves
Microwaves
Infrared (IR) Waves
Visible Light
Ultraviolet (UV) Light
X Rays
Gamma Rays

7. Electromagnetic Spectrum
All of the different kinds of light are examples of electromagnetic waves.
Electromagnetic Waves – A transverse wave consisting of oscillating electric and magnetic fields at right angles to each other.

8. Transverse Waves vs. Longitudinal Waves
Transverse waves oscillate perpendicular to the direction of the wave propagation.
Light Waves
Longitudinal waves oscillate parallel to the direction of the wave propagation.
Sound Waves
Link:
Transverse and Longitudinal Wave Animation

9. Electromagnetic Waves
Light is composed of electric and magnetic waves.
They are perpendicular to the direction they move.
They are transverse waves.
The electric and magnetic fields are at right angles to each other

10. Wave Differences
Electromagnetic waves are distinguished by their difference in frequencies and wavelengths.
They account for the color changes in visible light and distinguishes visible light from invisible electromagnetic radiation, such as X Rays.

11. Metric Prefixes

13. Speed of Light
All forms of electromagnetic radiation travel at a single high speed in a vacuum.
The speed of light in a vacuum was found to be x108 m/s
c = 3.00x108 m/s (speed of light)

14. Speed of Light = frequency x wavelength
Wave Speed Equation
c = fλ
Speed of Light = frequency x wavelength
Speed of Light (c) – Units are in (m/s)
Frequency (f) – Units are in (Hz)
Wavelength (λ) – Units are in (m)

15. Example Problem
What is the wavelength of infrared light with a frequency of 3.0x1012 Hz?

16. Example Problem Answer
λ = 1.0x10-4 m

17. Huygens' Principle The wave nature of light can be treated as a ray.
Treating the propagating wave of light as a straight line perpendicular to the wave front.

18. Brightness of Light The brightness of light depends on:
How much light is being emitted from the source.
Distance away from the source.

19. Brightness and Distance
Apparent brightness is proportional to the actual brightness of the source divided by the square of the distance between source and observer.
Lv = L/d2
Apparent Brightness = Actual Brightness ÷ distance2
Brightness – Units (cd) “candela”