light n.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Light PowerPoint Presentation
Download Presentation
Light

Loading in 2 Seconds...

play fullscreen
1 / 32

Light - PowerPoint PPT Presentation


  • 537 Views
  • Uploaded on

Light. Previous knowledge. Tell me one of your experience or vocabulary about light. What is light?. energy. Light is _______. Light travels in a _______ . Light consists of particles called _________. wave. photons. Light Spectrum. White light can be separated into 6 colors.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Light' - bernard-madden


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
previous knowledge
Previous knowledge
  • Tell me one of your experience or vocabulary about light.
what is light
What is light?

energy

  • Light is _______.
  • Light travels in a _______ .
  • Light consists of particles called _________.

wave

photons

light spectrum
Light Spectrum
  • White light can be separated into 6 colors.
  • The lowest frequency of light we can see with our eyes appears ______.
  • The highest frequency of light appear _______.

red

violet

electromagnetic waves e hf
Electromagnetic Waves(E=hf)

What characteristics of light determines the amount of energy carried by a photon of the light?

Frequency

slide6
E=hf
  • What is the frequency of a photon which has 4.41 x 10-19 J of energy? (Planck’s constant is 6.63 x 10-34 kgm2/s)
  • E=hf
  • Answer: 6.65 x 1014 Hz
transparent vs opaque
Transparent vs. Opaque
  • Transparent: Materials that allow light to pass through. Ex) water, glass, atmosphere
  • Opaque: Materials that do not allow light to pass through. Ex) wood, stone, metal, people
x rays
X-rays

Which part of a hand is opaque to x-rays? Skin or bone

Which part of a hand is transparent to x-rays? Skin or bone

the condition of transparency
The Condition of Transparency
  • A chain of absorption and re-emission
speed of light
Speed of light
  • Light travels at the speed of 3.00 x 108 m/s.
  • With this speed, light can travel from the sun to Earth in 8 minutes (about 500 seconds).
  • It takes 4 years for light to travel from the sun to the next nearest star in our galaxy.
  • Our galaxy has a diameter of 100,000 light-years.
slide12
v = f • λ
  • What is the frequency of a EM wave if it is a wavelength of 1000m?
  • 3.00 x 108 m/s = f • 1000
  • 3.00 x 105 Hz = f
slide13
v = f • λ
  • The AM radio station sends a radio wave of 1.0 x 106 Hz. What is the wavelength of this wave?
  • 3.0 x 108 m/s = 1.0 x 106 • λ
  • 3.0 x 102 m =λ
light slows down in glass or water
Light slows down in glass or water.

In water light travels at 75% of its speed or 0.75 c.

wave interactions
Wave Interactions
  • Waves can refract, or bend, as they change media.
index of refraction
Index of refraction
  • n = c/v
  • Index of refraction = speed of light in vacuum over speed of light in medium
  • n=1.333 (in water)
  • n=2.419 (in diamond)
snell s law
Snell’s law
  • ni(sin θi) = nr(sin θr)
  • Index of refraction of first medium x sine of the angle of incidence = index of refraction of second medium x sine of the angle of refraction

θi

θr

practice of snell s law
Practice of Snell’s Law
  • A light ray of wavelength 589 nm traveling through air strikes a smooth, flat slab of crown glass at an angle of 30.0 degrees to the normal. Find the angle of refraction.
  • (nair=1.00, nglass=1.52)
  • Answer: 19.2 degrees
critical angle
Critical Angle
  • At the critical angle, light beam no longer emerges into the air above the surface.
previous experience
Previous experience
  • How can you look at the back of your head?
flat mirrors
Flat mirrors
  • Light always travels in a straight line through a uniform substance.
  • If the surface is opaque, the light is deflected at the surface.
  • The change in the direction of the light is called reflection.
  • Specular reflection: reflected in one direction.
  • Diffuse reflection: reflected in many different directions
slide27

If a straight line is drawn perpendicular to the reflecting surface at the point when the incoming ray strikes the surface, the angle of incidence and the angle of reflection can be defined with respect to the line.

slide28
θ = θ’
  • Angle of incoming light ray = angle of reflected light ray
object distance image distance
Object distance, image distance
  • The relationship between object distance from the mirror which is represented as p, and image distance, which is represented as q, is such that the object and image distance are equal.
  • The image formed by rays that appear to come together at the image point behind the mirror – but never really do – is called a virtual image.
slide30

p (object distance) = q (image distance)

  • h (object height) = h’ (image height)

p

q

h

h’

polarization
Polarization

http://www.physicsclassroom.com/class/light/u12l1e.cfm for further information.

linear polarization
Linear polarization

The process that separate waves with electric-field oscillations in the vertical direction from those in the horizontal direction, producing a beam of light with electric-field waves oriented in the same direction.