It takes more refractive power to focus rays from a closer object since the rays are more divergent when they arrive at the lens. Since the nearsighted eye has excess refractive power that focuses parallel rays somewhere in the interior of the eye, bringing the object closer will cause the focal point to move toward the image-detecting retina and improve the vision. For the extremely farsighted eye above, things just go from bad to worse when you bring the object closer since you need more refractive power and you didn't have enough to begin with.
Thin Film Interference A film of thickness from 0.5 to 10 m is a transparent medium of glass, mica, air enclosed between glass, soap film, etc. When the light is made incident on this thin film partial reflection and partial refraction occur from the top surface of the film. The refracted beam travels in the medium and again suffers partial reflection and partial refraction at the bottom surface of the film. In this way several reflected and refracted rays are produces by a single incident ray. As they moves are superimposed on each other and produces interference pattern. Interference in Parallel Film ( Reflected Rays) Consider a thin film of uniform thickness ‘t’ and refractive index bounded between air. Let us consider monochromatic ray AB is made incident on the film, at B part of ray is reflected (R 1 ) and a part is refracted along BC.At C The beam BC again suffer partial reflection and partial refraction, the reflected beam CD moves again suffer partial