NAEST 2020 Image of an Arrow Formed by a Water Glass Lens Re

Question: Different light rays starting from the tip of the arrowhead go through the water and converge at one point (neglect aberration), somewhere between the water and the camera

1. in case-1 but not in case-2
2. in case-2 but not in case 1
3. both in case-1 and case-2
4. neither in case -1 nor in case-2

तीर के शिखर से चलने वाली प्रकाश की विभिन्न किरणें पानी से गुजरती है और पानी तथा कैमरे के बीच किसी एक बिंदु पर अभिसरित होती है (विपथन पर विचार न करें)

1. केस-1 में परंतु केस-2 में नहीं
2. केस-2 में परंतु केस-1 में नहीं
3. केस-1 और केस-2 दोनों में
4. न तो केस-1 में न हीं केस-2 में

Solution: Option (A) is correct.

Let us look at the glass of water from the top. It has two semicircular walls (of convex shape) with water-filled in its interior (refractive index 4/3). The water glass acts as a thick convex lens.

In case 1, the object (arrow) is far away from the glass. An inverted and magnified image of the object is formed. This is a real image formed by the water lens when the object is placed between F (focus) and 2F.

In case 2, the object (arrow) is placed closer to the glass. An erect and magnified image of the object is formed. This is a virtual image formed by the water lens when the object is placed between F (focus) and the optic center.

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