1 / 17

What is Light?

What is Light?. What is Light? Light is a kind of electromagnetic radiation. Light travels in transverse waves. Speed of Light (c) = 3.00 x 10 8 m/s (in a vacuum) That’s 186,000 miles per second.

camden
Télécharger la présentation

What is Light?

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. What is Light? • What is Light? • Light is a kind of electromagnetic radiation. • Light travels in transverse waves. • Speed of Light (c) = 3.00 x 108 m/s (in a vacuum) • That’s 186,000 miles per second At this speed light could travel the equivalent of 8 times around the world in one second!

  2. Light travels much faster than sound. For example: • Thunder and lightning start at the same time, but we will see the lightning first. • 2) When a starting pistol is fired we see the smoke first and then hear the bang.

  3. Practice Problem Ex. If a light wave has a frequency of 500,000 Hz, what is its wavelength? Given: F = 500,000 Hz λ = ? V = f λ 3.00 x 108 = 500,000 λ 600 m

  4. Electromagnetic Spectrum X-Rays Radiowaves Microwaves Ultra-violet GammaRays Infrared . Visible Light

  5. Radio Waves • Radio Stations, 2-way radio, remote controls, radar (navigation), listening devices (bugs) • Microwaves • Microwaves, Cellular phones, speed radars, Television, Ovens • Infrared • Movie – Predator, Police, Firemen, heating & air Electromagnetic Spectrum

  6. Electromagnetic Spectrum • Visible Spectrum – Light we can see • R OYGBIV • Largest to Smallest Wavelength. • Larger wavelength = Lower frequency = less energy • Shorter wavelength = Higher frequency = more energy

  7. UV light (Ultraviolet Light) • Sun, Tanning Beds, Black Lights • X - Rays • Medical x-rays, airport security, • Gamma Rays • Sterilizing Equipment, Cancer treatments, Electromagnetic Spectrum

  8. Short wavelength High frequency High energy Long wavelength Low frequency Low energy

  9. is the bending of the path of a light wave as it passes across the boundary separating two media. is caused by the change in speed experienced by a wave when it changes medium. Refraction

  10. When light travels from a less dense to • more dense medium (light slows down), • the ray is refracted toward the normal. • Example: light slows down when it passes from air into water • When light travels from a more dense • medium to a less dense medium (light speeds up), the ray is refracted away from the normal. • Example: light speeds up when passing from glass into air

  11. Index of refraction (n) Basically it says how hard it is for light to travel through a media. The higher the number the harder it is to travel. Index of refraction

  12. Snell’s Law: n1sin(q1) = n2sin(q2) • n1 = index of refraction of medium 1 • θ1= incident angle or θi • n2 = index of refraction of medium 2 • θ2=refracted angle or θr • To calculate: BE IN DEGREE MODE! Snell’s Law

  13. Practice A person is shinning a flashlight (through air 1.0) into an unknown medium (n2). The light enters at 28° to the normal line. It becomes 10 °within the 2nd medium. Calculate the index of refraction of the 2nd medium? 28o n1 = 1.0 air 10°o n2= ? 10o Snell’s Law Example

  14. Snell’s Law - Example n1 = 1.00 q1 = 28 ° q2 = 10 °θ n2 = unknown index • (1.00) sin(28) = n2 (sin 10) • 0.469 = n2 (0.174) • Divide by 0.174 • n2 = 2.70 • We can then check this value against the list of known refractive indexes and identify the material. n1sin(θ 1) = n2sin(θ 2)

  15. Index of refraction

  16. Given: ni = 1.00, nr = 1.33, θi = 45 ° Find θr Snell’s Law Example 45° • 1.00 * sine (45 °) = 1.33 * sine (θr) • 0.7071 = 1.33 * sine (θr) • 0.532 = sine (θr) • sine-1 (0.532) = sine-1 ( sine (θr)) • 32.1 ° = θr

  17. Index of refraction(n)=speed of light in a vacuum(c) speed of light in material (v) Index of refraction Another Equation … Practice Problem Calculate the speed of light in water. Water has an index refraction of 1.33. 1.33 = 3x108m/s n n =

More Related