1. Light

2. Light Facts
Visible Light is an electromagnetic wave that the human eye can detect.
Different light wavelengths are seen as different colors.
A ray is a straight line that represents the path of a light beam.
Speed of Light (c) = 3.0 x 108 m/s

3. Speed of Light
Physicist Albert Michelson determined the speed of light in the 1880s. He wanted to determine the speed of the “ether” through which light traveled.
His experiment showed that the speed of light is about km/s or 3.0 x m/s

4. Nature of Light Light has a dual nature because it behaves as both
a wave
a particle
Photons are bundles of electromagnetic energy that do not have mass
The wave nature of light can be seen from interference patterns. EM waves are transverse waves.

5. How is light like a wave?
Light reflects in the same manner a wave would.
Light refracts in the same manner a wave would.
Light diffracts in the same manner that a wave would.

7. Light will undergo interference in the same way a wave would.

8. Light exhibits the Doppler effect just as a wave would.

9. What happens when light reaches the end of a medium?
3 things will happen when light reaches the end of a medium.
1. Reflection: It bounces off an object
2. Refraction: If it approaches the boundary at an angle.
3. Diffraction: Boundary is an obstacle within the medium. And obstacle is smaller than wavelength.

10. 1. Reflection
Reflection: When an electromagnetic wave (or any other type of wave) “bounces” off of a surface. All waves show reflection.
Law of Reflection- when a light ray strikes a reflecting surface, the angle of reflection is equal to the angle of incidence. Ex . Laser beam

11. Regular vs diffuse reflection
Regular Reflection- when light rays are reflected in one direction. Ex. Smooth surface
Diffuse Reflection- when light rays are reflected in many directions. Ex Rough surface

12. Regular Reflection Example

13. Diffuse Reflection Example

14. 2. Refraction
Refraction: The bending of a wave as it passes from one medium to another medium. All waves refract when they enter new mediums
Refraction of light- bending of light due to the speed of light in different media. Ex Fish tank

15. Snell’s Law
Snell’s Law- a ray of light bends in such a way that a ratio of the sine of the angle of incidence to the sine of the angle of refraction is a constant.
ni sin I = nr sin r
n = the index of refraction of the medium
i = incident (“first”)
r = refracted (“second”)

17. Index of Refractions for various substances
Indices of Refraction
Medium n
Vacuum 1.0
Air
Water
Ethanol
Crown glass
Quartz
Flint glass
Diamond

18. 3. Diffraction
Diffraction is the spreading of waves into a space or region behind an obstacle.
Diffraction usually occurs when waves pass through small openings (like slits), around obstacles, or sharp edges
Diffraction occurs with all waves

19. Electromagnetic waves
An electromagnetic wave is (simplified) a self propagating wave that is part electric and part magnetic. It is caused by a moving charge.
The range of electromagnetic waves can be seen in the electromagnetic spectrum.
Notice the small portion that is visible light

20. EM wave

21. EM spectrum

22. Frequency will increase to right
Higher frequency = higher energy
Wavelength increases to left
Inverse Relationship
Broken up into sections
Visible light is only a small portion

23. Color
Colors of the spectrum are associated with specific light wavelengths
Primary colors – red , green , blue
Secondary colors – yellow, cyan, and magenta

24. The visible spectrum of Light

25. Calculation for spectrum
C=λv
λ lamda= wavelength
v = frequency of the light wave
c = speed of light (3x108 m/s)

26. Example
What is the frequency of electromagnetic radiation having a wavelength of 210 x 10-7 m.
1.4x10 13

27. EM Waves Radiation: the transfer of energy by EM waves
High frequency EM waves have the greatest amount of energy
High frequency EM waves behave like a photon and are high energy waves
Low frequency EM waves behave more like a wave and are lower energy waves
Visible light is the only part of the EM spectrum that humans can see

28. Polarization
The aligning of vibrations of a transverse wave. This is usually accomplished by filtering.
Example: polarized sun glasses.

29. Polarization of light
Polarization of light – light in which the electric fields are all in the same line.Light can be polarized because it is a transverse wave.
Ex. Sunglasses

30. Common conversions 1 MHz = 106 Hz 109 nm = 1 m 100 cm = 1 m
1000 g = 1 kg
1000 m = 1 km

31. Light and Matter Transparent- objects that transmit light waves
Ex. Glass, plastic,
Translucent – transmit light but objects are not seen clearly. Ex. Frosted glass
Opaque- absorb or reflect all light waves that fall on them. Ex. Brick

32. Index of Refraction and Speed of Light
The index of refraction is the ratio of the speed of light in a vacuum to the speed in the medium.
Equation: nsubstance = c / vsubstance or
vs = c / ns