# Only one problem

1. Apr 24, 2004

### mustang

Problem23. A grating with is illuminated with light of wavelength 585 nm. What is the highest order number that can be observed if the grating has 1483 lines/cm? remember sin(theta) can never be greater than 1.

2. Apr 24, 2004

### gnome

C'mon. Just plug into the formula.

He gave you λ and it takes just one division to find d. You know that sin(ANYTHING) can't be greater than 1. So what is the biggest integer m that gives you a sin less than 1? Then there's just 1 more step. I'm sure you can figure that out.

3. Apr 24, 2004

### mustang

m*(585 nm)
sin(theta) = 1 = ------------
6743 nm/line

Multiply both sides by 6743 to get:

6743 = m * 585

Then divide both sides by 585 to get:

m = 6743/585 = 11.5
But when i checked the asnwer was wrong?

4. Apr 24, 2004

### gnome

Is 11.5 an integer?

5. Apr 24, 2004

### mustang

What are you trying to say in "Is 11.5 an integer?"

6. Apr 25, 2004

### gnome

Let's take it one step at a time.

Do you understand what the lines represent?

In other words, do you realize that the lines appear on the viewing screen only at points where light rays coming through different slits interfere constructively with each other?