# Where does dispersion actually take place?

Out of 1 & 2, which is most accurate?
And, out of 3 & 4, which is most accurate?
Do they both agree with each other?

• Well you would need to know what the refractive index of the triangle and the ambience is Apr 20, 2019 at 12:35
• @Maxim assume that the two prisms have same R.I. Apr 20, 2019 at 12:39
• So in the constellation of 3&4: If the refractive index doesn't change it is basically the same material for the EM wave. So does the EM wave change at the transition? Apr 20, 2019 at 12:43
• @Maxim That's my point, if 1 is true then no problem but if 2 is true how is 3 and 4 possible how does light come to know whether its entering a prism or a glass slab Apr 20, 2019 at 12:54
• Is the incoming wave one single wavelength or a superposition of many many different wavelengths? Apr 20, 2019 at 12:58

I assume that the incoming light is a superposition of many different wavelengths and since the refractive index depends on the wavelength $$n = \frac{k}{2 \pi} \cdot \lambda,$$
where $$\lambda$$ is the wavelength. So if you have many different wavelengths they will all travel in different directions, Answer to your first and second question.