Posted by **physics** on Saturday, March 14, 2009 at 12:56pm.

Monochromatic light from a helium-neon laser (wavelength=632.8 nm) shines at a right angle onto the surface of a diffraction grating that contains 130 960 lines/m. Find the angle at which one would observe the first-order maximum.

formula: (a+b)Sin theta = n wavelength

(a+b) = 1

____ m; n=1

wavelength=632.8*10^-9 m

=6.328*10^-7m

Sin theta=6.32^8 * 10^-7 * 130960

= 6.328*10^-7*130960*10^5

theta= 4.7536deg

= 4.75

is this done correctly?

130960

- physics -
**drwls**, Saturday, March 14, 2009 at 1:15pm
I don't know what a and b are supposed to be in your diffrection grating formula. The correct form of the quation is

d (sin i + sinr) = m*lambda

where i and r are the angles of incidence and reflection.

In your case sin i = 0, m = 1, and d is the grating line separation, which is your case is 1/(130960m^-1) = 7.636*10^-6 m.

Therefore

d sin r = 632.8*10^-9 m

sin r = 632.8*10^-9*130960 = 0.08287

r = 4.75 degrees

So you got the right answer, anyway

## Answer this Question

## Related Questions

- physics - pleaase help me with this, i'm very bad in physics, and i mostly don't...
- PHYSICS - 1) A diffraction grating with 2.500 x 10^3 lines/cm is used to examine...
- Physics - I'm working on a final physics exam, and I've got everything but these...
- physics - A diffraction grating gives a second-order maximum at as angle of 31...
- physics - A diffraction grating gives a second-order maximum at as angle of 31...
- Physics, diffraction, interference, help! - 3.Blue light (λ = 450 nm) ...
- physics - Why is white light separated into a spectrum of colors when it is ...
- Physics - The light shining on a diffraction grating has a wavelength of 470 nm...
- physics - a laser beam with wavelength 632.8nm is incident normal to the plane ...
- Physics - Light of wavelength 600 nm illuminates a diffraction grating. The ...

More Related Questions