# All Questions

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### Change of a lens' focal point with wavelength. Refractive index wavelength independent

I was using a Comsol example for the focusing lens: https://www.comsol.com/model/focusing-lens-57621 I made no changes to the model. The focal length of the lens is set to be 1000 um. Initially, I ...
144 views

### Fourier transforming properties of a converging lens

Following Goodman's Introduction to fourier Optics argument I understand that a converging lens will introduce the following difference in optical path (see pag.158, 4th edition) $$r^2/2f$$ where $r$...
169 views

### Can a lens be used at radio frequency?

Lenses and Antennas are two means of manipulating EM waves. While antennas are predominantly used at RF / Microwave frequencies, Lenses are used for optical/IR regions of the spectrum. I understand ...
507 views

### Why does a Fraunhofer diffraction pattern appear on the focal plane of a lens?

How do implement the information that behind the aperture/slit/crystal plane there is a focusing lens in the Fresnel-Kirchhoff integral? It seems that the solution is understanding the role of the ...
4k views

### Intensity of light after it passes through a convex lens [closed]

When a parallel beam of light falls on a convex lens and get converge to its focus, does the intensity of light change?
2k views

### Question about lens maker's formula

I am trying to follow the derivation of lens maker's formula from the textbook "University Physics", p.1133 (https://books.google.com.hk/books?id=nQZyAgAAQBAJ&pg=PA1133#v=onepage&q&f=false)...
526 views

### What wavelength of light is the term 'focal length' defined against? [closed]

Because different wavelengths of light are bent differently in a medium, the focal length ought to be different for each of them (which is why white light splits up into a rainbow). If I have a "25 mm ...
826 views

### Can a magnifying glass work on EM radiation other than visible light?

A magnifying glass is a convex lens which allows us to bend visible light, thus the image of the object appears larger. My question is, can a magnifying glass work on the rest of the electromagnetic ...
1k views

### How do I find the right lens for my laser?

I purchased this line laser recently and I'm running into a bit of an issue. The laser shoots out at a 120 degree angle which is perfect. However, once the laser spreads to about 4.25 inches, I need ...