# What is Optic lens: Definition and 21 Discussions

The optic nerve, also known as cranial nerve II, or simply as CN II, is a paired cranial nerve that transmits visual information from the retina to the brain. In humans, the optic nerve is derived from optic stalks during the seventh week of development and is composed of retinal ganglion cell axons and glial cells; it extends from the optic disc to the optic chiasma and continues as the optic tract to the lateral geniculate nucleus, pretectal nuclei, and superior colliculus.

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1. ### I Why is Cherenkov radiation blue? And what about refractive index?

I got this question from my son last night. If you Google "Why is Cherenkov radiation blue", you get this: Somewhat more substantial is the Wiki article on the Frank-Tamm formula. That formula ties the Cherenkov radiation wavelengths to the transmission characteristics at any specified...
2. ### The patient is myopic

Its near point is 13.0 cm from the eyes and its far point is 50.0 cm. a) What type of contact lenses should be prescribed to correct his nearsightedness. Determine their focal length b) Determine the near point of the patient when using lenses for the correction of myopia.
3. ### I Difference between Working distance and object distance

So I have a problem understanding the difference between working distance and the object distance of a lens. For me it is also unclear what the difference between image distance and back focal length. If I want to enlarge the image by 6. How can I calculate the focal length, object distance...
4. ### Approximating the Edge of a Lens as a Prism

Hello there, for part a. of this problem I thought I should try to find the radius of curvature R of the lens using the Lensmaker's Formula. Then it would be quite easy to find the minimum thickness T by just finding the thickness of the circle segment using Pythagoras' Theorem. But part of...
5. ### Imaging optics and lowest possible angle video projection?

I have a very very unusual project requirement where I need a pocket video projection with the lowest possible projection angle or "longest possible throw-ratio". It's a pocket DLP projector so goal is to have the beam remain ,as much as possible, almost the same size as the DLP matrix, for a...
6. ### Must we always use absolute value for lens magnification?

My brother's physics teacher says that magnification and height of image are always positive. Is she right?
7. ### Does the picture change if we turn a thin lens around

Hello, suppose we are given a thin lens and consider an image of some object formed by that lens. I am wondering what would happen to the image if the thin lens is flipped around (180 degrees)? Of course, if the lens is perfectly symmetric -like for a bi-konvex lens- then the picture should not...
8. ### Principal plane of a thin lens

Hello, in geometric optics people usually say that the refraction of light beams due to a thin lens can be handled by introducing a hypothetical plane (the so called principal plane) at which all the refraction can be considered to happen. But most books only picture the situation for symmetric...
9. ### Image if a mirror is placed at the focal distance of a biconvex lens

Hello, suppose we are given a biconvex lens with focal length of 4 cm. Further, an arrow of height 1 cm is placed in front of the lens in a distance of 8 cm (i.e. twice the focal length). Lastly, a mirror is placed on the other side of the lens at a distance of 4 cm and such that it performs an...
10. ### Optics: Half Lens in the Air, Half Lens in Water.

Homework Statement Hello everybody! One surface of a biconvex lens (n=1,5) is in the air (na=1) while the other surface is dipped in the water (nw=4/3). If the power of the lens in the air is Po=10 Dioptri, The lens power in such condition is? Homework Equations Lensmaker Equation...
11. ### I Minimum deviation in prism spectroscope

Suppose that I use a prism (vertex angle ##\alpha##) spectroscope to analyze a beam of visible light from a mercury lamp (different wavelenghts) and I want the determine the refraction index of the prism using the minmum deviation angles ##D_{min}##...
12. ### Ray diagram diverging lens both object and image virtual

Homework Statement Draw the ray diagram of the case of a diverging lens where both object and image are virtual, that is ##f<0## , ##p<0## with ##p<f## Homework EquationsThe Attempt at a Solution I did not find this particular case of ray diagram in any textbook so I would like to know where...
13. ### B Angle of vision for a real image

Hi there, i want to know as much as possible about this situation. I want to know the angles of vision for a real image, where can one see the image, the location of our eye to see it. Which factors determine this angle Thank you so much :D I hope this isn't a dumb question, thanks.
14. ### Not a homwork problem, Fresnel Equations

Homework Statement I was just curious, I know you can derive the critical angle using Snell's law..but could you use it using the Fresnel Equations of reflection, both of them? Homework Equations |r|=1 internal reflection of light...
15. ### Image Distance with two concave lenses

Homework Statement An object 1.25 cm tall is placed 100 cm in front of a convex lens with a focal length of magnitude 50 cm. A concave lens with a focal length of magnitude 20 cm is placed 90 cm beyond the first lens. Where is the final image located? Homework Equations (1/s)+(1/s')=1/f s=...
16. ### Effect of Collimated lens on Gauss Beam

Hello everyone, I am trying to find effect of collimated lens on gaussian beam propagation. Do you know how to solve that? I need any equations ,then going to use them via matlab. Thanks
17. ### Image of an Object Inside Hollow Glass Sphere

Hello, This question is from 1990 Turkey National Physics Olympics. I tried my best to translate it clearly. 1. Homework Statement https://s23.postimg.org/cotn29afv/Hollow+Spherical+Glass.jpg The sphere of radius 2R has an empty sphere inside with radius R. In order for the image of an object...
18. P

### Lens basic question....

Why does a ray of light change's it's direction as it passes the lens? It's because of the fermat principle? Is because of the index of refraction? (Why there is no index of refraction in 1/p + 1/q = 1/f ?)And if it's because of the index of refraction can we apply snell law? Once the ray passes...
19. ### Optic lens to collimate/focus light from a LED.

Hello. I'm looking for a lens that can collimate (or focus far away >500mm ) a light coming out from a LED. before I give more details is this even possible? Thanks.
20. ### Solving Optic Lens Problem: Find Object Distance for Magnification of 75

Homework Statement Suppose we have a microscope made out of two lenses, both with a focal length of 25mm, placed 36.5mm apart. Find how far in front of the first lens should the object be placed to assure that the image is magnified at least by a factor of 75? One more: Suppose that...
21. ### Find Focal Length of Lens When Moving From 20cm to 15cm

If a lens is moved towards the object from a distance of 20cm to 15cm, the magnification of the image remains the same. What is the focal length of the lens? Sorry I am new here so please forgive me if I have violated any rules.:cry: