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# Waves and optics(1)

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### Waves and optics(1)

1. 1. Waves and Optics Nisha Issac (: & Ethan Munguia
2. 2. Interference <ul><li>When two waves pass through the same region of space at the same time </li></ul><ul><li>2 types: </li></ul><ul><ul><li>Constructive: crest to crest; larger amplitude </li></ul></ul><ul><ul><li>Destructive: crest to trough; resultant is zero if both the waves have same amplitude. </li></ul></ul>
3. 3. Diffraction <ul><li>Refers to the ability of waves to bend around obstacles </li></ul><ul><li>Amount of diffraction depends on the wavelength of the waves and the size of the obstacle. </li></ul><ul><li>In the case of narrow opening, the amount of bending increases as the size of the opening decreases. </li></ul>
4. 4. Dispersion of light <ul><li>Spreading of white light </li></ul><ul><li>Dispersion of light in a transparent material occurs because the index of refraction of the material varies the wavelength. </li></ul><ul><ul><li>Index of refraction is higher for shorter wavelengths </li></ul></ul>
5. 5. Electromagnetic Spectrum <ul><li>Radio waves, Microwaves, Infrared, Ultraviolet, X-Rays, Gamma Rays </li></ul>
6. 6. Reflection <ul><li>“ Bouncing” off of a wave of a surface; exact angle </li></ul><ul><li>Angle of incidence = Angle of reflection </li></ul><ul><li>The angle of incidence is the angle that light is striking a surface. The angle of reflection is the angle that the light is reflected, or bounced </li></ul>
7. 8. Refraction <ul><li>Change in direction of a wave when it passes into a new substance </li></ul><ul><li>Reason it changes direction or bends is because each different substance has its own effect on speed of light. </li></ul><ul><li>Index of refraction- Equals the ratio of speed of light in a vacuum to the speed of light in a transparent substance. Determines the angle of bending of the light at the interface between two transparent substances. </li></ul>
8. 9. Mirrors <ul><li>Reflective surfaces </li></ul><ul><li>Convex and Concave </li></ul><ul><li>Has a focal point, where all the light directed at that mirror converges or diverges and the distance between the mirror and that point is the focal length. </li></ul>
9. 10. Lenses <ul><li>Has a focal point </li></ul><ul><li>Focal point of the lens- point where rays parallel and very close to the principal axis all pass through after refraction by the lens. </li></ul><ul><li>Focal Length- distance from the center of lens to focal point </li></ul><ul><li>Radius of curvature of a lens is exactly twice the focal length. </li></ul>
10. 11. Important Formulas <ul><li>θ = the angle of spread of a wave after passing through a single slit opening </li></ul><ul><li>λ = wavelength </li></ul><ul><li>fn = the nth frequency in a series of resonant frequencies </li></ul><ul><li>v = speed of the wave </li></ul><ul><li>L = length </li></ul><ul><li>D = width of an opening through which a wave will diffract </li></ul>
11. 12. Example #1 <ul><li>A ray of light strikes the surface of a flat glass plate at an incident angle of 30(degree). The index of refraction of air and glass are 1.00 and 1.50, respectively. Determine the a) angle of reflection and b) angle of refraction. </li></ul><ul><li>Answer: </li></ul><ul><ul><li>The reflected ray follows the laws of specular reflection and so the angle of reflection is 30 degrees </li></ul></ul><ul><ul><li>Snell’s law; 19 degrees </li></ul></ul>
12. 13. Example #2 <ul><li>A laser beam is incident on 2 slits separated by .500mm. The interference pattern is formed on a screen 1.00m from the slits & the 1 st fringe is found to be .120cm to the right of the central maximum. A) Calculate the wavelength of the light in nm & b) determine the maximum number of bright fringes that can be observed. </li></ul><ul><li>Answers: </li></ul><ul><ul><li>A: 6.00 x 10 -7 </li></ul></ul><ul><ul><li>B: m=833 </li></ul></ul>
13. 14. Example #3 <ul><li>A radar pulse travels from Earth to the moon & back in 2.60 secs. Calculate the distance from the Earth to the moon in a) meters and b) in miles </li></ul><ul><li>Answers: </li></ul><ul><ul><li>d= 3.90 x 10 8 m </li></ul></ul><ul><ul><li>d= 2.42 x 10 5 miles </li></ul></ul>