A thin concave (diverging) lens is held 18 ,cm in front of a small candle flame
PHYSICS · Multi-part · CBSE · Physics · Light — Reflection and Refraction · Light — Reflection and Refraction
Problem
A thin concave (diverging) lens is held 18\,cm in front of a small candle flame. An eye is positioned on the same side of the lens as the candle so that the flame is viewed through the lens.
Answer the following questions about the image that the observer perceives.
(1) Describe qualitatively how at least two distinct rays originating from the tip of the candle flame travel through the lens and reach the observer’s eye so that the brain perceives an image. Your description should identify the direction changes at the lens and indicate where the rays appear to originate after passing through the lens.
(2) The image distance si produced by the lens carries a negative sign, whereas the given object distance so is positive. Explain the physical meaning of the negative sign for si in this context.
(3) Using physical reasoning, explain why the image formed by the concave lens cannot be captured on a screen placed in any location, yet is still visible to the observer.