# An experiment using a diffraction grating with

1. Jan 7, 2017

### Hoyin

1. The problem statement, all variables and given/known data
An experiment using a diffraction grating with a monochromatic light source is performed to create an interference pattern on a screen.

Consider the following changes:
I. Increase the line density of the grating.
II. Decrease the frequency of the source.
III. Increase the distance to the screen.

2. Relevant equations
Which of these changes would cause the pattern to spread out?
a) I only b) III only c) I and III only d) I, II, and III e) None of these changes

3. The attempt at a solution
Looked up intensity but that's different from amplitude and I didn't get the rest

2. Jan 7, 2017

### blue_leaf77

The diffraction formula for the location of a particular fringe is
$$d \sin \theta = m\lambda$$
By inspecting this equation, you should be able to find the answer.

3. Jan 7, 2017

### goodphy

Hello.

I recommend you to look at the diffraction grating equation.

The diffraction grating equation is y = (m*λ*D)/d, y is the distance between intensity peaks at m and m = 0 orders, λ is a wavelength of light incident on the grating, D is the distance between the grating and a screen, d is a slit separation distance.

The question "which of these changes would cause the patterns to spread out" is reinterpreted as "which factors make increase of y". At a single λ, according to the equation, increasing m and D increases y. decreasing d also results in increasing y. So, the answer is "d)".

I don't understand "3. Looked up intensity but that's different from amplitude and I didn't get the rest".