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Saturday, 31 October

JEE Main 2020 · PhysicsNumerical answerNumerical valueHardMulti-step

JEE Main 3 September 2020, Shift 1, Physics Q24

Question 24 of 75 in this shift, Physics question 24 of 25.

An observer can see through a small hole on the side of a jar (radius 15 cm) at a point at height of 15 cm from the bottom (see figure). The hole is at a height of 45 cm. When the jar is filled with a liquid up to a height of 30 cm the same observer can see the edge at the bottom of the jar. If the refractive index of the liquid is N/100, where N is an integer, the value of N is __________.

The figure, in words

An eye is drawn at the upper left; a straight ray with an arrowhead runs from a point on the right wall of an open rectangular jar (a short hatched strip drawn on the right wall from the bottom up to that point, 15 cm above the bottom) up and to the left, passing through the hole at the top of the left wall, and on to the eye. A dashed horizontal line marks the top of the jar; short vertical lines extend above the jar's walls. Labels: 45 cm (double-headed vertical arrow on the right, spanning the jar height from bottom to the dashed line), 15 cm (vertical arrow marking the height of the point on the right wall above the bottom), 15 cm (horizontal arrows below the jar spanning only the right half of the bottom, from about its midpoint to the right wall).

Official answer

158.00

NTA final key (Sep 2020).

Chapter
Ray Optics and Optical Instruments
Topic
Refraction and Snell's Law
Idea tested
Snell's Law Application

Same idea in other shifts

Asked 4× in all
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  2. 6 Apr 2023, Shift 1 · Q52A pole is vertically submerged in swimming pool, such that it gives a length of shadow 2.15 m within water when sunlight is incident at an…HardNumerical value
  3. 27 Jun 2022, Shift 1 · Q47Consider a light ray travelling in air is incident into a medium of refractive index 2n\sqrt{2n} . The incident angle is twice that of…MediumSingle correct

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. This question needs a figure we do not reproduce; it is described in words above. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.