The optimal object placement for a lens with a focal length of 0.3m is indeed at the focus, which is 0.3m away from the lens. When the object is positioned at this focal point, the rays of light passing through the lens become parallel. These parallel rays then reflect off a plane mirror placed 0.2m behind the lens and return through the lens, converging to form an image that coincides with the object's position. This phenomenon is explained using ray diagrams and the thin lens formula.
PREREQUISITESStudents studying optics, physics educators, and anyone interested in understanding the principles of lens and mirror interactions in optical systems.
If the object is at the focus, what can you say about the rays from a given point on the object after they have passed through the lens?phantomvommand said:Homework Statement:: A lens has a focal length of 0.3m. A plane mirror is placed 0.2m behind the lens. Where must an object be placed, for its image to coincide with its position?
Relevant Equations:: Ray diagrams
thin lens formula
Apparently, it must be placed at the focus (0.3m away from the lens). Why is this so?
Won't the rays that emerge from the lens all be parallel to each other? But the rays hit the mirror at different points. How will the reflected paths then reconverge to form the image?haruspex said:If the object is at the focus, what can you say about the rays from a given point on the object after they have passed through the lens?
Follow their path on to the mirror and back through the lens.
I see what you mean. Thank you very muchharuspex said:If the object is at the focus, what can you say about the rays from a given point on the object after they have passed through the lens?
Follow their path on to the mirror and back through the lens.