Lightsorce through spectrometer

[SwedishFred]

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

 

[SammyS]

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.

 

[TSny]

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?

 

[SwedishFred]

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

 

[SammyS]

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?

 

[SwedishFred]

((3.33*10^-6)*(sin24.5))/2
((3.33*10^-6)*(sin24.5))/3
Red 690nm
Blue 461nm

True ?