# Reflection and Refraction Ranking by Phase Shifts

• bokonon
In summary, the conversation discusses the presence of phase shifts in refracted and reflected rays when a ray of light is incident onto an interface between two different materials with different indices of refraction. The first part of the question asks to rank scenarios based on the phase shift in the refracted ray, while the second part asks to rank scenarios based on the phase shift in the reflected ray. The speaker also mentions the intuitive understanding of bigger differences in indices of refraction leading to greater phase shifts, but acknowledges their confusion on how this works. It is explained that the phase shift for reflected rays is determined by the interface between fast and slow mediums, while for refracted rays, it should depend on the difference in indices of refraction. However, the
bokonon
1. A ray of light is incident onto the interface between material 1 and material 2. There is a figure, which is a standard figure of a ray in medium of n1 striking an interface where medium2 (with n2) meets medium1. As is typical, some of the light is reflected and some is refracted.

The question asks: Given the indices of refraction n1 and n2 of material 1 and material 2, respectively, rank these scenarios on the basis of the phase shift in the refracted ray. And then goes on to list different scenarios (e.g n1=1.33, n2=1.46 vs n1=1.33 n2=1.0).

The second part is the same, but asks to rank based on the phase shift in the REFLECTED ray.

2. This question is a lot different from standard ray optics questions, and I wonder why there is any phase shift at all, unless the refracted ray meets another interface where it can reflect/refract and thenTHAT reflected ray would have a phase shift from the first refracted ray, because it has traveled a different distance through medium 2. But how can you compare the phase shifts of two different refracted rays? I feel like I am missing something. Any suggestions? Thanks.

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There is no phase shift as a ray is transmitted into a new medium. There is a phase shift when the ray is reflected in certain conditions. Do you know what those conditions are?

So you're saying that the answer to the first part of the question is that all of the different conditions for the indices of refraction make no difference, as no refracted rays experience a phase shift?

I'm thinking for the reflected rays there is a phase shift when n2>n1, intuitively I'd guess that the bigger the difference the greater the phase shift, but I can't picture how this works at all. If the rays are all just bouncing off the interface, then why would there phases change?

The phase shift is either 180˚ (1/2 wavelength) or none at all. It is determined by the interface being fast to slow, or slow to fast mediums.

"The phase shift is either 180˚ (1/2 wavelength) or none at all. It is determined by the interface being fast to slow, or slow to fast mediums."

You're speaking strictly about reflected rays, right? I'm still confused about why there are any phase shifts at all.

Thanks

bokonon said:
You're speaking strictly about reflected rays, right? I'm still confused about why there are any phase shifts at all.

Thanks
So are we all. The mechanical wave (wave on a string) has a simple explanation
http://www.kettering.edu/~drussell/Demos/reflect/reflect.html

the reason why light also does the same, even one photon at a time, requires knowledge of quantum electrodynamics (QED). Just let it go for now ;-)

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A good investigation into phase shift, will show that for the REFRACTION (that is, the transmitted ray), the phase shift should depend on (n2-n1), so any variety of interfaces can easily be ranked. Of course, the distance/time in the medium and the wavelength of the light.

Here is one set of lecture notes which goes further into this topic http://www.physics.pdx.edu/~larosaa/Ph-223/larosa_lecture10_ph_223.pdf

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MP123

## 1. What is the difference between reflection and refraction?

Reflection is the bouncing back of light or sound waves when they hit a surface, while refraction is the bending of light or sound waves as they pass through a medium.

## 2. How are reflection and refraction related to phase shifts?

Phase shifts occur when there is a change in the wavelength or frequency of a wave due to the interaction with a medium. In reflection, there is no phase shift as the wave simply bounces off the surface. In refraction, the wave experiences a phase shift as it enters a new medium with a different density, causing it to change direction and speed.

## 3. How do we rank reflection and refraction by phase shifts?

We can rank reflection and refraction by the amount of phase shift that occurs. Reflection has a phase shift of 0 degrees, while refraction has a phase shift that varies depending on the angle of incidence and the refractive index of the medium.

## 4. What is the significance of understanding phase shifts in reflection and refraction?

Understanding phase shifts in reflection and refraction is important in many scientific fields, such as optics, acoustics, and electronics. It allows us to predict how waves will behave when interacting with different materials, and also helps us to design and optimize various devices and technologies.

## 5. Can phase shifts be observed in everyday life?

Yes, phase shifts can be observed in everyday life. For example, when looking at an object through a glass of water, the object appears to be in a different position due to the refraction of light. Additionally, when you hear an echo, it is due to the reflection of sound waves off of a surface, causing a phase shift in the wave.

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