Physics Help Forum intresting question on plano concave lens
 User Name Remember Me? Password

 Light and Optics Light and Optics Physics Help Forum

 Feb 28th 2010, 09:54 AM #1 Banned   Join Date: Jul 2009 Posts: 66 intresting question on plano concave lens ) The plane side of a thin plano-convex lens is silvered. Will it act as a convex or concave mirror? Justify your answer by drawing a ray diagram. The material of lens has refractive index 1.5. What is the radius of curvature of the curved surface of lens if the focal length of the mirror is 40 cm? I am hung in 2 paramers R1 and R2 in formula 1/f=(mu-1)(1/R1 +1/R2 )
 Feb 28th 2010, 11:01 PM #2 Senior Member   Join Date: Dec 2008 Location: Udupi, Karnataka, India Posts: 292 If a parallel beam of light fall on the plano-convex lens what happens to the rays? After reflation from the mirror in the backside what happens to the reflected rays? This will decide the nature of the silvered plano-convex lens.
 Feb 28th 2010, 11:51 PM #3 Banned   Join Date: Jul 2009 Posts: 66 I wonder you are adding me more confusion by questioning or giving way of solution.
Mar 1st 2010, 02:14 AM   #4
Senior Member

Join Date: Dec 2008
Location: Udupi, Karnataka, India
Posts: 292
 Originally Posted by binayakafle I wonder you are adding me more confusion by questioning or giving way of solution.
Instead of giving away the solution directly, I am directing you towards the answer. Just try to answer the questions in my post. Use Snell's law.
Keep in mind one thing. If the emergent rays from the lens are converging, the image is real. Otherwise the image is virtual.

 Mar 1st 2010, 09:01 AM #5 Banned   Join Date: Jul 2009 Posts: 66 And what about 2nd part of my question.
 Mar 2nd 2010, 12:40 AM #6 Senior Member   Join Date: Dec 2008 Location: Udupi, Karnataka, India Posts: 292 When a parallel beam of light falls on it, before converging to a point, it refracts twice through the lens and reflects once from the mirror. If you consider the point of convergence as focus of the system, then 1/F = (μ-1)/R + (μ-1)/R. (μ-1)/R is the focal length of the lens.

 Tags concave, intresting, lens, plano, question