3 - Interference and Diffraction. Coherence of Light

Question 1

What are the equations for intensity from diffraction and interference?

Answer 1

g(x) = ((sin(a * x))/(a * x))^2

h(x) = cos^2(b * x)

Question 2

What is the Rayleigh Criterion?

Answer 2

It is a formula for calculating the smallest angle that a telescope will be able to resolve.

Theta* = 1.22 * lambda / d

Question 3

What is angular resolution?

Answer 3

Angular resolution describes the ability of any image-forming device such as an optical or radio telescope, a microscope, a camera, or an eye, to distinguish small details of an object, thereby making it a major determinant of image resolution.

Question 4

What is the coherence length?

Answer 4

Delta x = c / (Delta f)

Question 5

What is coherence?

Answer 5

Coherence is an ideal property of waves that enables stationary interference. Two wave sources are coherent if their frequency and waveform are identical.

Question 6

How do you determine if two wavelengths can be resolved?

Answer 6

Using,

R = lambda / Delta * lambda = n * N

If a second wavelength is less than the sum of lambda + Delta * lambda then it cannot be resolved in that system.

Question 7

How can you change a system set up to make two wavelengths resolve?

Answer 7

Increasing the number of slits, N, increases the angle of diffraction and reduces the value of Delta * lambda