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Relationship between the power of a convex lens and the refractive index of a medium

According to the Lensmaker's formula, $$\frac{1}{f} = (μ-1)\left(\frac{1}{R_1} - \frac{1}{R_2}\right)$$ Apparently, focal length $f$ is inversely proportional to the refractive index of the medium $μ$. Since, Optical Power $P = \frac{1}{f}$. This should imply that optical power is directly proportional to the refractive index. However, today I got...

Why does the sky after sunset mimic the blackbody spectrum?

There are several answers on this site and elsewhere about why the sky is blue and why sunsets are reddish. But I could not find anything that discusses the relationship between the blackbody spectrum and the spectrum of colors seen above the horizon after sunset. In particular, the "physical spectrum" (meaning the set of colors seen in the sky...

Why do colours change in water

I was doing my swimming rounds, when it turned dark, so the pool management turned on the lights. The lights were actually yellow in colour, but they appeared green if I moved far away from them underwater(6 to 7m). They looked yellow above water. Someone please explain this.

A unique phenomenon related to shadows [duplicate]

yesterday I was creating shadows with my hands and observed this - when i bring 2 fingers very close to each other and see its shadow on screen the fingers are distant in real but their shadow kind of bends . this is how(please see picture below).. can someone please explain it. its just out of curiosity.

What is the spacing between interference fringes?

In this problem, we are trying to determine the spacing between interference fringes for a setup of two optically flat glass plates with a small wedge of air between them. I am attaching a screenshot from a video here (the link is below as well). The person making the video is showing that he derived the equation (distance = number of fringes * wavelength)...

Must the distance between the reflectors of a coherent laser be a multitude of its intended wavelength?

Must the distance (aka cavity length $L$) between the two reflective mirrors of a spatial and temporal coherent laser be a multitude of the lasers intended wavelength? If no, why not? If yes, how does changing the cavity length $L$ of the mirrors affect the temporal coherence (or phase)?

How do the evanescent waves contribute/cause a diffraction limit?

In the following article, under the section Physics of the Superlens, it is stated: The light emitted or scattered from an object includes not only propagating waves but also evanescent waves, which carry the subwavelength detail of the object. The evanescent waves decay exponentially in any medium with a positive refractive index so that they...

How does LIGO work?

LIGO is described as working as an interferometer, like a Michelson-Morley interferometer but with many reflections along the arms to increase the sensitivity. In MMs work it was assumed that the mirrors were held in a rigid relationship and so differences in light speed along the orthogonal arms would show up as a phase shift. But in LIGO the mirrors...

The Michelson-Morley experiment (fringe shift)

What i don't understand about the experiment is why wasn't the first calculated path drift $ds$ enough but they had to rotate the expiriment by 90 degrees and calculate $dx= ds- ds'$? (Where the $ds'$ is the second calculated path drift). If there as a difference between the fringes wasn't the first calculation enought?

What's the track it will be for light?

Let's suppose one shaking light starts from Proxima Centauri and travels toward the earth. We know light will travel from more 4 years to reach the earth. It will be interesting if we 'look' at the travelling light in space (suppose we can), the light should be shaking in space, shouldn't it? we will see a shaking light, or a bending light. However,...

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