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Assertion (A) : We cannot… (Class 12 Physics 2025, Q15)

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PhysicsCBSE Class 12 · Board exam 2025, set 55/1/1 · 1 mark · Assertion-reason

CBSE Class 12 Physics 2025: question 15

Set in the CBSE Class 12 board exam of 2025, paper 55/1/1, section A, question 15, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q15 · 1 mark · Assertion-reasonCompetency-basedSemiconductor Electronics: Materials, Devices and Simple Circuits

Assertion (A) : We cannot form a p-n junction diode by taking a slab of a p-type semiconductor and physically joining it to another slab of a n-type semiconductor.
Reason (R) : In a p-type semiconductor while in a n-type semiconductor .

  1. (A)Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
  2. (B)Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
  3. (C)Assertion (A) is true, but Reason (R) is false.
  4. (D)Assertion (A) is false and Reason (R) is also false.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 55/1/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

Check the majority carriers in a p-type semiconductor.

Hint 2

Why can two slabs not simply be joined?

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. A is true: physically joining two slabs leaves surface roughness far larger than the interatomic spacing, so there is no continuous junction.

    ½ mark

  2. R is false: a p-type semiconductor has , and an n-type has , which is the opposite of what R states. Option (C).

    ½ mark

Answer: Option (C)

Where the marks are

  • Judges A true and R false (reversed carrier concentrations) (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Semiconductor Electronics: Materials, Devices and Simple Circuits, one at a time, marked against the answer key and marking points.Back to the full paper2025 board paper, set 55/1/1: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.