Question

1. A slit is illuminated first by red light, then by blue light, which color will spread out the most? Explain. 2. Two source (A and B) of red light (650 nm wavelength) destructively interfere on a screen. An observer sees a dark spot on the screen. What difference in a path (in nanometers) could account for this? Explain. (delta L = BC - AC)

Answer 1

1. This is a simple diffraction phenomenon and can be explained by formula of maxima in single slit diffraction.

The relevant formula is where a=slit width, = angle of diffraction or SPREAD, m= order of diffraction

From the above equation you can see that _red > _blue as _red > _blue So lager spread out can be observed in RED LIGHT.

2. For destructive interference of light the path difference = odd multiple of /2

i.e.    so _minima = = 325nm (when m=0)