Spherical lens v/s Cylindrical lens | Lens identification made easy

Lens identification is an important task in optics and can be done using various methods. One way to identify different types of lenses is by observing the movement of an image as it passes through the lens.
A convex lens is thicker at the center than at the edges and converges light rays towards a focal point. When an object is placed in front of a convex lens, the image formed is real, inverted and smaller than the object. As the object moves closer to the lens, the image moves away from the lens. Conversely, as the object moves away from the lens, the image moves closer to the lens.
On the other hand, a concave lens is thinner at the center than at the edges and diverges light rays away from a focal point. When an object is placed in front of a concave lens, the image formed is virtual, upright and smaller than the object. As the object moves closer to the lens, the image moves closer to the lens. Conversely, as the object moves away from the lens, the image moves away from the lens.
A cylindrical lens, also known as a cylindrical or astigmatic lens, has a curved surface in one direction and a flat surface in the other direction. It is used to correct astigmatism, a condition where the cornea of the eye is not perfectly spherical. When light passes through a cylindrical lens, it is bent more in one direction than in the other direction. This causes the image to be distorted and appear elongated in one direction.
In conclusion, lens identification can be done by observing the movement of an image as it passes through the lens. A convex lens converges light rays towards a focal point, while a concave lens diverges light rays away from a focal point. A cylindrical lens has a curved surface in one direction and a flat surface in the other direction, causing the image to be distorted.
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[@Dr.Doaa11]

Very helpful &simplified, thanks too much

[@eishashoaib4728]

Who can someone be so perfect to convey concept every single time 🥹

[@InsightOphthalmology]

That's really sweet of you to say 😊

[@steffiroseprasad6051]

Maam, really love your videos
Making concepts crystal clear ..

[@sajid-khan77]

Very nice and informative but here I will ask for some extra explanation.
Q1:what is the reason and concept behind the WITH and AGAINST motions of the concave and convex lenses respectively.
Q2:in this video you have shown only convex cylinder and concave cylinder movements along their power meridian which is understood, my question is how to identify the movement in spherocylindrical lenses ie plus spher with plus cylinder, minus sphere with minus cylinder, plus sphere with minus cylinder and minus spher with plus cylinder.

[@InsightOphthalmology]

With and against movement can be explained by the way rays of light are focussed and the vergence of rays.Rays coming from the object through a concave lens are diverging rays and focus behind an observer so we see with movement. Contrary to that the rays from object on passing through a convex lens are more converging and focus before an observer .This gives against motion to the image.
Now this is more easy to understand with visualisation
You can try watching our video on retinoscopy basics to understand this principle 😊
ruclips.net/video/Sdai6Nfw6LY/видео.html

[@sajid-khan77]

@@InsightOphthalmology thanks for this

[@hamadmbarouk880]

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[@MukeshKumar-pj8re]

GOOD EXPLANATION MAAM...❤❤

[@idiwani5590]

Plz make a video on contact lenses😊

[@otiebrown9999]

Good review.
Thanks

[@uzairjatt7065]

Please mam make video on cataract surgeries

[@HananHan-y4l]

Very helpful video. Thanks Dr.

[@InsightOphthalmology]

Most welcome!

[@bloodshredder1982]

Really insightful video

[@InsightOphthalmology]

Glad you liked it

[@Priyachakma.R]

Explain so well ❤

[@InsightOphthalmology]

Thanks a lot 😊

[@TheSingingSingh874]

Thanks Dr👍👏

[@malyajtiwari5793]

Thanks man

[@InsightOphthalmology]

No problem

[@sk-fs2em]

Thank you somuch mam 😊

[@dilipdamordamor4520]

Govt job ke liye kuch Requirement rahti hai kya..

[@khaledking5408]

Thank you so much

[@InsightOphthalmology]

Soon

[@musikaaffection8570]

thank u so much mam

[@TheSingingSingh874]

Thanks

[@nadeem9692]

❤❤

[@cozwhynot58]

❤

[@skzubair0124]

Very deeply and easily explanation mam TQ for such videos.iam bsc optometry student

[@InsightOphthalmology]

Glad it helped :)