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NATURE OF LIGHT

NATURE OF LIGHT

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NATURE OF LIGHT

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  1. NATURE OF LIGHT

  2. WHAT IS LIGHT?

  3. Light What is it? How does it behave when it interacts with objects in the environment? Why does it produce the effects we see?

  4. LIGHT IS A DIFFERENT FORM OF ENERGY WAVE

  5. Light does not require a medium Electromagnetic waves do not need a medium Move by changing the electric and magnetic fields in space Light is the most widely known electromagnetic wave

  6. Light and all other electromagnetic waves slow down in denser mediums Adsorption and readmission by each particle

  7. Absorption then readmission

  8. DOES LIGHT MOVE AS PARTICLES OR IN WAVES?

  9. PARTICLE RAY CHARACTERISTICS OF LIGHT

  10. The path of light

  11. Other evidence that light moves in rays Hold two books parallel to the ground, slightly apart, one on top of the other

  12. Shadows Some of the light is blocked by the book

  13. Shadows

  14. Observations of light Moves away in all directions away from both luminous and illuminated sources Can treat motion of light in a specific medium as particles moving in a straight line within a medium

  15. Light can be modeled as a stream of “particles” These “particles” are called photons Do not have mass Packets of energy Moves in a straight line in a medium

  16. WAVE LIKE CHARACTERISTICS IN LIGHT

  17. Light can be modeled as a wave A lot of the characteristics could be explained using either model The spreading out in all directions Reflection off of opaque surfaces Bending through transparent surfaces Plus…

  18. Diffraction The bending of the waves around a barrier The wave interacts with the barrier slowing down the part of the wave that touches it The waves stay in the same medium For light to diffract the wavelength of the light must on the same scale as the opening

  19. Difference in light moving as particles or waves

  20. Dispersion The separation of white light into many colors due to the bending of light Rainbows, light through prisms, oil spills…

  21. Corona’s around the moon Light passing between drops in clouds

  22. Light produces interference patterns like water waves

  23. Color Each color a different wavelength

  24. Scientist have not determined if light is only a wave or particle They currently accept either of models, depending on the situation

  25. The nature of light Light has both wave-like and particle like characteristics in its motion and interaction with the environment. Wave characteristics: diffraction, interference, dispersion, color Particle characteristics: moving in straight line, shadows

  26. VARIATIONS OF LIGHT

  27. ELECTROMAGNETIC SPECTRUM

  28. Electromagnetic Spectrum Visible light make up just a small part of the range of light waves, just like audible sound does in the range of sound frequencies. Electromagnetic spectrum consists of light at all possible energies, frequencies and wavelengths. The properties of light change as its frequency changes

  29. Electromagnetic spectrum

  30. Similarities of waves All move at the same speed in a certain medium v=λƒ All move by being absorbed and the readmission to the environment All do not need a medium to move from place to place

  31. Differences • All have different wavelengths/frequencies • The amount of energy possessed is different: Higher frequency light indicates Higher energy Gamma Rays have most Radio Waves have least • The interaction between wave and medium is not constant throughout the spectrum

  32. Regions of electromagnetic radiations

  33. Regions of the spectrum Gamma rays have the largest frequency (therefore, smallest wavelength) Small enough to pass through most parts of body without meeting anything In x-rays, those that hit bone are absorbed, and do not hit the photographic plate (dark and light parts)

  34. X-ray image

  35. The good and bad of gamma and x-rays High energy Interaction may kill living cells or alter them fatally Can also be used to kill cancerous cells a form of “ radiation therapy”

  36. Radiation Therapy

  37. Ultraviolet light Smaller frequencies than x-rays but more than visible light This is the portion of light spectrum that causes sunburn, even on cloudy days

  38. Sunbathers

  39. Birds, Bees, Flowers and Tress A number of Flora and Fauna utilize Ultraviolet light Bees see UV light which helps them use the sun on cloudy days for guidance. Different flowers have UV colors in addition to visible colors for further identification Definitely birds and possibly deer also see into the UV range

  40. Visible light Infrared light (showing what would be detected) UV light (showing what would be detected)

  41. Infrared light Frequencies of light slightly smaller than visible light All matter warmer than absolute zero gives out infrared or “radiant heat” Can be sensed by some living beings Infrared cameras, heat seeking missiles Snakes hunt using infrared receptors

  42. Infrared uses

  43. Microwaves and Radio waves Microwave, Radio and TV waves are the largest in wavelength, smallest in frequency Boundary between types is arbitrary

  44. Microwaves Microwaves are reflected by metals pass thru air, glass, paper plastic absorbed by fat, water and sugar Energy of wave passes into food, makes molecules vibrate- heat up

  45. Uses of microwaves

  46. Mobile phones Use microwaves to transmit information Least effected by surroundings