A bunch of rays are incident on a concave surface from the left, as in the Figur

Question

A bunch of rays are incident on a concave surface from the left, as in the Figure below. The rays appear to be converging to a point (S) 20 cm right of the vertex, V. The radius of curvature of the concave surface is 15 cm. a. Where would the rays meet after refracting from the interface? The refractive indices are as shown in the Figure. (5 marks) 01 b. What happens if we block half of the interface with an absorptive material that prevents any light from going through, as shown below? (2.5 marks) 022 absarphve hiçht- black maleri

Explanation / Answer

a. from the given data
   we can assume object to be a point virtual object to the right of the lens
   so object distance u = 20 cm
   focal length = R/2
   R = radius of curvature, R = 15 cm
   hence f = 7.5 cm

   so, from thin lens formula
   1/v - 1/u = 1/f
   1/v = 1/7.5 + 1/20
   V = 5.454 cm
   hence the image is formed to the right of the lens at x = 5.454 cxm away form the lens

b. when we block half lens with some material, the final positon of the image does not change but the intensity of the image reduces by half as half the light coming from thje source is not reaching the image point

c. if we block small volume around S, even then the images will converge at the calculated point as the virtual object doesnot have to be present in the locaitonfor the image to form

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