10propertiesoflight-140123181500-phpapp02.pdf
- 2. Properties of Light • Effects of Materials on Light • Reflection • Refraction • Dispersion • Total Internal Reflection • Interference • Diffraction • Scattering of Light • Polarization
- 3. Effects of Materials on Light Materials can be classified based on how it responds to light incident on them: 1. Opaque materials – absorb light; do not let light to pass through 2. Transparent materials – allow light to easily pass through them 3. Translucent materials – allow light to pass through but distorts the light during the passage
- 4. Reflection Light follows the Law of Reflection: “The angle of incidence is equal to the angle of reflection.” Light can bounce off materials in two ways: 1. Diffuse reflection – reflected rays go in different directions; happens in rough- textured or uneven surfaces 2. Regular/Specular reflection – reflected rays go in one directions; happens in smooth and shiny surfaces; image can be seen
- 5. Refraction Light bends/refracts when it changes speed. This usually happens when the light travels from one medium to the next. Simple rule of thumb in refraction: • If light slows down, it will refract towards the normal line. • If light speeds up, it will refract away from the normal line.
- 6. Refraction Light travels faster in air, slow in water and slower still in glass. The slower light is in a medium, the more it refracts/bends in it. The measure of how much light refracts in a medium is called index of refraction. Medium Index of Refraction (n) air 1.000293 water 1.3330 glass 1.490 diamond 2.419
- 7. Refraction Light follows the Law of Reflection: “The angle of incidence is equal to the angle of reflection.” Light can bounce off materials in two ways: 1. Diffuse reflection – reflected rays go in different directions; happens in rough- textured or uneven surfaces 2. Regular/Specular reflection – reflected rays go in one directions; happens in smooth and shiny surfaces; image can be seen
- 8. Refraction Light follows the Law of Reflection: “The angle of incidence is equal to the angle of reflection.” Light can bounce off materials in two ways: 1. Diffuse reflection – reflected rays go in different directions; happens in rough- textured or uneven surfaces 2. Regular/Specular reflection – reflected rays go in one directions; happens in smooth and shiny surfaces; image can be seen
- 9. Dispersion The process in which light is separated into its colors due to the differences in degrees of refraction. How are rainbow s formed?
- 10. Total Internal Reflection When light is reflected completely at the boundary between two mediums How do fiber optics work? Why do diamonds
- 11. Diffraction Light spreads out after passing through/by an opening /edge. The opening must be very narrow for diffraction of light to occur. “Every cloud has a silver lining.”
- 12. Interference Light can superimpose and have either constructive interference or destructive interference.
- 14. Reflection • Reflection - Light bounces off the surfaces like mirrors such that the angle of incidence is equal to the angle of reflection. • Refraction - Refraction is defined as the bending of light as it passes through materials of different optical density • Interference - When two light waves meet or coincide, it can create either constructive or destructive interference based on how the crests & troughs of the waves meet.
- 15. Wave Properties (Light) • Diffraction - This is defined as the bending of light waves around obstacles in its path. Example, when a light wave passes through a barrier with a small opening, it acts as a single point source from where light emerges and spreads in all direction.
- 16. • Light has a dual nature. • Depending on the phenomenon or behavior in question, light can be treated either as a wave or as a particle. • To examine this wave-particle duality, we will examine two experimental proofs. So, is light a wave or a particle?
- 17. • Conducted by Thomas Young in the early 1800’s • Provided an experimental basis for considering light as a wave. Light is a WAVE: Young’s Double-Slit Experiment
- 18. • The individual slits acted as individual sources which light passes through and spreads. (Isn’t this like water waves?) • Light exhibits interference which is a wave property. Key Points of Young’s Experiment
- 19. • Explained by Einstein during the early 1900’s • Provided an experimental basis for considering light as a particle. • Einstein earned a Nobel Prize for his explanation. Light is a PARTICLE: The Photoelectric Effect
- 20. • Higher energy light knocks off electrons at higher energy. • The number of ejected electrons is directly related to the intensity (brightness) of light. This means brighter lights emit more photons. • Light is a particle since it is capable of ‘knocking off’ electrons. Further, unlike waves, increasing the brightness does not increase the energy of the knocked off electrons. Key Points of Photoelectric effect