Lesson on Properties of Light in Grade 7

This is a ppt presentation on the lesson about light.

1. Properties of Light
•Waves, particles and EM spectrum
•Interaction with matter
•Absorption
•Reflection, refraction and
scattering
•Diffraction and polarization

2. EM Wave

3. Light waves
Complex light
Single wave =
monochromatic
light
Coherent light =
laser
Polarized light

4. Electromagnetic
spectra
High frequency EM
acts like a particle
Low frequency EM
acts like a wave

5. Interaction with matter
•Color occurs when molecules selectively
absorb light of specific wavelengths
•High energy, short wavelengths, disrupts
chemical bonds
•Infrared radiation affects bond vibrations
and is perceived as heat (snakes, vampire
bats have heat sensors, but poor resolution)
•Light is selective absorbed and reradiated in
a transparent medium

6. Requirements for Vision
•Reflection off solid objects
–Higher and lower frequencies pass through
•Straight-line transmission without scatter
–Permits formation of spatial maps
•Refraction at the boundary of two media
with different densities
–Permits focusing and image formation by an
eye behind a lens

7. Absorption depends on wavelength

8. Absorption depends on frequency

9. Water absorbs red faster than blue

10. Speed of light depends on media
Speed of light is slower in water than in air (opposite to sound)

11. Light reflects and refracts
air
water
Snell’s law = n
1sinq
1= n
2sinq
2where n
i= refractive index

12. Refraction
http://micro.magnet.fsu.edu/primer/java/refraction/index.html

13. Reflectance
Diffuse (dull, matte) Specular (shiny)

14. Large angle causes internal reflections
air
water
cell

15. Scatter depends on wavelength

16. Sun is yellow, sky is blue

17. Polarized Light
http://micro.magnet.fsu.edu/primer/java/polarizedlight/filters/index.html

18. Polarized light indicates solar position

19. Refraction depends on frequency

20. Lenses focus light
http://micro.magnet.fsu.edu/primer/java/magnify/index.html

21. Mammalian Eye

22. Far and near sightedness

23. Light Diffraction
http://webphysics.ph.msstate.edu/javamirror/ipmj/java/slitdiffr/

24. Color

25. Color Spectra

26. Color has 3 dimensions

27. Light interference