Lightsorce through spectrometer

  • Thread starter Thread starter SwedishFred
  • Start date Start date
  • Tags Tags
    Spectrometer
Click For Summary

Homework Help Overview

The discussion revolves around a problem involving light diffraction through a spectrometer with a grating of 300 slits/mm. Participants are tasked with determining the wavelengths of red and blue light that coincide at a deflection angle of 24.5°, while noting that no order number (n) is provided.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants calculate the grating spacing (d) and apply the diffraction equation d*sinα=n*λ to find the wavelengths. There is discussion about the validity of using non-integer values for n, with some participants questioning whether two different wavelengths can share the same n value.

Discussion Status

Some participants have provided calculations for the wavelengths and discussed the implications of using non-integer values for n. There is an acknowledgment that n must be an integer, leading to further exploration of the correct integer values for n corresponding to the red and blue wavelengths.

Contextual Notes

Participants note the lack of explicit information regarding the order number (n) and the implications this has on the calculations. There is also a mention of potential confusion regarding the terminology used, such as "gitter" being interpreted as "grating."

SwedishFred
Messages
28
Reaction score
0

Homework Statement


A light hits a spektrometer perpendicular into a gitter with 300 slits/mm. You observes that a red and a blue line (in Visual light) coinciding. And the angle deflectionis 24.5°. What wavelength have the red and the blue lines.
No n is given.

Homework Equations


d*sinα=n*λ

The Attempt at a Solution


First i calculated d
1/300000m = 3.33*10-6
((3.33*10-6)*(sin24.5))/625-9 http://www.dramaten.se/Repertoar/-Ungefar-lika-med/ 2.5

((3.33*10-6)*(sin24.5))/500-9 http://www.dramaten.se/Repertoar/-Ungefar-lika-med/ 2.5

Answer:
so the red wavelength is 625nm
so the blue wavelength is 500nm
n=2.5

Is this correct ? can it be 2.5?? the blue is closer to n3 and red n2
 
Physics news on Phys.org
SwedishFred said:

Homework Statement


A light hits a spektrometer perpendicular into a gitter with 300 slits/mm. You observes that a red and a blue line (in Visual light) coinciding. And the angle deflectionis 24.5°. What wavelength have the red and the blue lines.
No n is given.

Homework Equations


d*sinα=n*λ

The Attempt at a Solution


First i calculated d
1/300000m = 3.33*10-6
((3.33*10-6)*(sin24.5))/(625*10-9) http://www.dramaten.se/Repertoar/-Ungefar-lika-med/ 2.5 , (I get ≈ 2.2)

((3.33*10-6)*(sin24.5))/(500*10-9) http://www.dramaten.se/Repertoar/-Ungefar-lika-med/ 2.5 , (I get ≈ 2.7)

Answer:
so the red wavelength is 625nm
so the blue wavelength is 500nm
n=2.5

Is this correct ? can it be 2.5?? the blue is closer to n3 and red n2
So, I take it that "gitter" is "grating".

I get approximately 2.2 and 2.7 as shown above in RED.

So, yes, use n = 2 for red & n = 3 for blue.
 
Hello, SwedishFred.

You know that n must be an integer, so n cannot be 2.5. Think about this: Is it possible for two different wavelengths to overlap using the same value of n for each wavelength?
 
TSny said:
Hello, SwedishFred.

You know that n must be an integer, so n cannot be 2.5. Think about this: Is it possible for two different wavelengths to overlap using the same value of n for each wavelength?
No that was what i was thinking about, so I understand it now, its much easier to see it happened ;-)
Thanx
 
SwedishFred said:
No that was what i was thinking about, so I understand it now, its much easier to see it happened ;-)
Thanx
What do you get for the two wavelengths?
 
((3.33*10-6)*(sin24.5))/2
((3.33*10-6)*(sin24.5))/3
Red 690nm
Blue 461nm

True ?
 
Last edited:

Similar threads

Diffraction Grating Angle Between Second Order Maxima
  • · Replies 1 ·
Replies
1
Views
11K
Egg tossing crime -- From what location was the egg thrown?
  • · Replies 14 ·
Replies
14
Views
3K
Questions about diodes, relativity, radiations
  • · Replies 1 ·
Replies
1
Views
5K
Mathematica This Week's Finds in Mathematical Physics (Week 259)
  • · Replies 1 ·
Replies
1
Views
4K