physics diffraction light fringes slits?

Question

a screen containing 2 slits 0.100 mm apart is 1.2 m from th viewing screen. LIght of wavelength is 400 nm *violet light* falls on the slits from a distant source.
a. approx how far apart will the interference fringes be on the screen?
b. if instead wavelength= 700 nm *red lights* how far apart will interfernece fringes be?
c. describe what would be seen if white light was used ?

please help test tomorrow

Answer 1

As always, Wikipedia has the answer. In fact, it appears twice in the article. The first time with a hard to read font, the second under the heading "Results observed":
http://en.wikipedia.org/wiki/Double-slit_experiment

The equation is nw = xb/L where:

n is the peak number (0 for the central peak, 1 for the two flanking peaks, etc.)
w is the wavelength of the light
x is the physical distance from the central peak
b is the separation between the slits
L is the distance from the slits to the screen center

The key to getting the right answers is to make sure all the units are compatible.

Answer 2

i prefer to declare which you will not even use easy bulbs. you may purely use coherent easy, which quantities to lasers. in many situations the slits are so close that a prevalent laser's diameter is considerable sufficient to disguise the two slits. in addition to, the laser easy is in section with itself. 2 distinctive lasers could be out of section, producing a random development first of all. the concept which you will shine an quite centred laser on one slit, and a 2d centred laser on the different slit to offer an interference development can't paintings. you may say definitively that this photon went by using this slit, and that one went by using the different slit. as a effect, you get what you anticipate : bullets. You get 2 vivid spots at the back of each and every slit. yet once you may not say the place each and every photon went then that's reported to have long gone by using the two and interfered with itself. subsequently, your interference development with one million easy source and a pair of slits. i'm undecided what might ensue in case you had 2 particularly extensive unfold laser beams whose beams the two strike the two slits. As I reported, the two distinctive beams could be out of section with one yet another. this could regulate the place the extrema ensue, yet there could nonetheless be some (the prospect being a undeniable section which forces each and every thing to combine to form a relentless, so which you get a single dim line of persevering with intensity). you may not administration the element of each and every laser, and by using risk with one million laser that section is irrelevant. that's spoke of as an "absolute section."