About Interference?

Question

Two rays of light from the same source destructively interfere in their path lenghts differ by how much?

and I need to demonstrate the wave properties of light in the lab by using a slit film with different slit patterns with a range of widths, spacing, and number of slits. Before I go, I just want some ideas of how it's going to be resulted.

1)when two waves interact, do you end up with a larger amplitude wave, a small amplitude wave, or no amplitude?

2)What conditions d oyou need to make a larger amplitude wave?

3) what would show that light has wave properties?

4) Figure out, using geometrical arguments, whereyou should see bright spots and where you should see dark spots.

5) would the same concepts hold for sound waves and water waves?

Answer 1

Two waves of light from SAME source do not show intereference. Two coherent waves destructively interfere when they arrive at a point in opposite phase(.when path difference between them is odd number multiple of half wavelength i.e.path difference=(2n+1)wavelength lambda / 2

According to superposition principle,

1)When two waves superpose, the resultant amplitude A is a vector sum of individual amplitudes a(!) and a(2)
A=square root of[a(1)square+a(2)square+2a(1)a(2)cosine of phase angle between them ]
The resultant amplitude is maximum when phase difference is zero or both are in same phase.
The resultant amplitude is minimum when both are in opposite phase.
The resultant amplitude is zero when a(1)=a(2) and both are in opposite phase.
2)The resultant amplitude is larger if phase angle is between zero to 90 degree
3)Interference , diffraction show that light is a wave
4)if 'd' is separation between the two coherent sources and theta is the angular position of the point under consideration (w.r.t.the origin i. e. the mid point between the sources)
then for bright spot, the path difference d sin theta is either zero or integral multiple of wavelength lambda

For dark spot, the path difference is odd multiple of HALF wavelength.

5)same concepts hold for all waves (light,sound ,water)

Answer 2

Nice try -- I'm still not going to do your homework for you.