# All Questions

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### Why does violet light bend the most? [duplicate]

When white light passes through a prism, refraction occurs and it splits into its seven constituent colours. If the spectrum is obtained on a screen violet light appears much more bent than red light. ...
65 views

### Do gravitational waves disperse/refract (like EM waves in a prism)?

I have read this question: What is the relationship between a gravitational wave and a graviton? where kingledion says: Gravitational waves were theorized a century ago and recently ...
41 views

### Why does the intensity of the scattered light vary when a monochromatic laser is shined into a transparent object?

When a laser is shined into a glass ball such as this video (link) or a bottle of water (link) the light is refracted through the whole transparent body. However, the intensity of the light scattered ...
4k views

### Why doesn’t a normal window produce an apparent rainbow?

When light refracts in a prism it creates a rainbow. My question is, why don’t all windows or transparent objects create this dispersion, i.e. why is the refractive index dependent on frequency in a ...
85 views

### What does it mean to say that glass has refractive index 1.5?

The refractive index of a material depends on the wavelength of the light incident upon it which is why dispersion happens. When we say that glass has refractive index 1.5 which wavelength do we have ...
62 views

### Speed of electromagnetic wave [closed]

On dispersion , speed of wave is inversely proportional to its wavelength . Therefore, gamma has max speed. But then in visible light , violet has least wavelength still it has least speed in visible ...
33 views

### How does refractive index increase in anomalous dispersion?

Refractive index generally increases with decrease in wavelength but in anomalous dispersion it decreases with decrease in wavelength. What causes it to be like that?
139 views

### What really is the speed of light in a medium/vacuum, group or phase velocity?

While reading about refractive index 2 terms popped up, group velocity which alway slows down in a medium and phase velocity which may exceed speed of light. Say in a complete vacuum and using laser ...
50 views

### If the velocity of light is different in different medium is it wavelength changes or frequency changes?

We know that the velocity of light is equal to the product of it's wavelength and frequency. And when light goes from vacuum to any other medium it's velocity changes depending the mediums refractive ...
222 views

### In refraction how does light interact with electrons if it is not absorbed? [duplicate]

What I (think I) understand: When light is refracted in a medium (say glass), the light interacts with the electrons in the medium and the electrons create new waves. Summing the waves with the ...
963 views

### Refractive index and wavelength relation [duplicate]

In general, the refractive index of a certain medium tends to decrease with increasing wavelength. But are there any materials in which the opposite phenomenon occurs? That is, in which the ...
94 views

### Is there a way to explain a rainbow in an almost-QM-correct way to a 5 year old child?

My toddler asked me "how does rainbow happen", and I would like to give a pedagogical explanation of the relation of photon frequency, its color, and the way different frequencies are bent in a drop ...
462 views

### Why do high frequencies have a larger deflection through a prism than smaller frequencies? [duplicate]

The following is a proof that higher (angular) frequencies have a greater deflection than lower frequencies through a glass prism: It was omitted in the image above, but $n_{\text{air}}$ is taken to ...
906 views

### Why is the speed of light the same for all colors in a vacuum but different depending on the color when light goes through a non-air medium?

I know that red light travels faster in non-air mediums than blue light because of its wavelength, but I'm not understanding why this doesn't happen in a vacuum? This is related to the topic of ...
2k views

### Why do convex lenses not disperse light like prisms, given that entry and exit points aren't parallel?

I understand that light entering a parallel block of glass at a non-90 degree angle will cause dispersion of colours within the block but that these will be refracted by the same degree upon exit so ...
524 views

### Order of colors after reflection in a raindrop

I studied two figures of sunlight reflecting in a raindrop: In the first image, red is shown above violet, but in the second image, red is below violet. Are both cases possible?
47 views

### How to obtain the dispersive refractive index of a sample in a Michelson interferometer from the interferogram?

In the Michelson interferometer setup shown below, first I obtain the interferogram of the source (without sample). Then I put in the sample. If the sample is not dispersive (its refractive index is ...
117 views

### Speed of the color red

Taking aside all of the other variables that can alter the color's speed; i.e. sound, mass, water, magnetism. And just focusing on the color itself, how fast does the color red travel, using the means ...
710 views

### Why is rainbow always circular?

From the article that I read on physics classroom website on rainbow, rainbow is formed with red on the top and violet on the bottom because violet refracts more, and has a smaller angle of deviation ...
780 views

### Refraction of white light through a glass slab: what does it actually look like?

When a collimated beam of white light enters a rectangular prism, it develops slightly coloured edges due to the dispersive refraction of the glass: each ray in the beam is displaced differently ...
847 views

### Refractive index and electric susceptibility

Suppose we have a complex refractive index $n_{ref}=n+ik$ whose value is given at a precise frequency $\omega_l$ from experimental data. We know that the imaginary part is responsible for the loss/...
2k views

### Frequency dependence of the speed of light in air

According to this link, the speed of light of different colors in a medium should be different. But if the refractive index of light in air is 1 then this means that the speed of light in air and ...
2k views

### Which electromagnetic radiation is faster in water, microwaves or light?

Well I've been asked this question, but I haven't been able to come with an answer yet using books and some web searches. The point is as the title says, to answer the question with the whole ...
1k views

### Why does the speed of the Electromagnetic wave in the material depend on the frequency of the wave where as they are constant in vacuum (freespace)? [duplicate]

I am confused on why would the propagation speed of any EM waves at ANY frequency is constant in the free space (vacuum) but they seem to disperse in any other materials as the propagation speed of EM ...
429 views

### Absorption of waves in a plasma

Suppose a plasma has characteristic frequency $\omega_p$. Since $$n = \sqrt{\left(1-\frac{\omega_p^2}{\omega^2}\right)}$$ For $\omega<\omega_p$, the refractive index will be imaginary - which ...
32k views

### On what refractive index of medium depends ? [duplicate]

does the refractive index of a medium depends on wavelength of light passing through it ? If yes then why ?
777 views

### Dispersion relation of silicon

In the case of dispersion relation of silicon having crystal plane orientation 111; what is the Sellmeier's equation for refractive index $n$ of silicon orientation 111 & what it's extinction ...
3k views

### Two different mediums can have equal index of refraction?

In other words: given a certain medium, is light's phase velocity unique?