1 / 11

Light is a Wave

Light is a Wave. Blue light = 4500 Å. Red light = 6000 Å. 1 Nanometer = 10 -9 Meters. 1 Angstrom = 10 -10 Meters. Waves. wavelength. crest. Frequency = 1/Wavelength Measured in Hertz (Hz) = 1/Seconds. amplitude. trough. Compression & Displacement. Interference.

neith
Download Presentation

Light is a Wave

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. Light is a Wave Blue light = 4500Å Red light = 6000Å 1 Nanometer = 10-9Meters 1 Angstrom = 10-10 Meters

  2. Waves wavelength crest Frequency = 1/Wavelength Measured in Hertz (Hz) = 1/Seconds amplitude trough

  3. Compression & Displacement

  4. Interference • In phase addition of two waves gives a third wave with an amplitude equal to the sum of the first two waves • Out of phase addition of two waves gives a third wave with an amplitude equal to the difference of the first two waves • Green and Red are the first two waves, black dots are the result after addition • For two equal waves: • In phase produces third wave of twice the amplitude • Out of phase produces third wave with zero amplitude

  5. Is Light a Particle or a Wave? • It's both! • In certain experiments light acts as a stream of particles (photons) bombarding a surface • In other experiments light must be considered as a wave traveling through space • Amplitude corrisponds to brightness • Light is a “displacement wave” although it requires no medium to travel through • Wavelength determines the color of the light, λf = c

  6. Diffraction: Circular Aperture A = 2.44λ/D A is the angular diameter of the Airy Disk, λ is the wavelength of the light, D is the diameter of the pinhole The wavelength of the light we’re using is 675 nm (6.75 x 10-5cm)

  7. Linear Size of the Airy Disc • We know A = 2.44/D • If s is the diameter of the disk and l is the distance from the pinhole to the image: • A = s/l from the small angle approximation • s = 2.44l/D s l

  8. Diffraction Terms • Constructive Interference leads to bright spots on the screen where the amplitude is increased • Destructive Interference leads to dark spots on the screen where the amplitude is decreased • As the aperture decreases in size the central bright point (Airy Disc) increases in size and decreases in power: it looks bigger and fainter • This leads to smaller telescopes, i.e. smaller apertures, having poorer resolution than larger telescopes • Resolution defines how close objects can be together and still appear as separate objects

  9. Diffraction: Slit Aperture s = nl/2D l is the distance from the slit to the image D is now the width of the slit n is an integer: If n is odd, it is the distance to a bright fringe If n is even, it is the distance to a dark fringe NOTE: n=1 corresponds to the central fringe

  10. Diffraction: Double Pinhole D s/3 Screen l s = l/D D is the distance between the two pinholes s is the spacing between two adjacent fringes l is the distance from the pinholes to the image

More Related