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#physics MCQ

15 public questions tagged with this topic.

Atomic Models - Rutherford, Thomson and Bohr

Which of the following statements is incorrect about the hydrogen atom’s energy levels in Bohr’s model?

**Rutherford's nuclear model** atom has small massive positively charged nucleus with electrons orbiting, size ratio atomic to nuclear ~10⁵, nucleus ~10⁻¹⁵ m atom ~10⁻¹⁰ m, most alpha particles with large impact parameter pass undeflected, small fraction >90° scatter from close approach, centripetal force provided by Coulomb attraction k Z e²/r², fails to explain stability because accelerating charge should radiate and collapse. Energy levels are discrete and negative, becoming less negative with increasing n , not positive or continuous as in classical models. Using E_n = -13.6/n² eV, r_n = n

Ref: NCERT > Physics Book > Atoms and Nuclei > Atomic Models - Rutherford, Thomson and Bohr

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PHYSICS

Which of the following equations is dimensionally inconsistent?

(a) [v] = [L T^{-1], [u + a t] = [L T^{-1] + [L T^{-2] [T] = [L T^{-1], consistent. (b) [s] = [L], [v t + a t] = [L] + [L T^{-1], inconsistent. (c) [F] = [M L T^{-2], [m v² / r] = [M L² T^{-2] / [L] = [M L T^{-2], consistent. (d) [E] = [M L² T^{-2], [F r] = [M L T^{-2] [L] = [M L² T^{-2], consistent.

Ref: NCERT Physics Textbook for Class XI and XII, Chapter: Units and Measurements and Physical World, Topic: Dimensional analysis and fundamental principles.

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PHYSICS

In forward bias, the effective barrier height of a p-n junction is:

In forward bias, the applied voltage ( V ) opposes the built-in potential ( V_0 ), reducing the effective barrier height to V_0 - V, allowing more carriers to cross the junction.

Ref: NCERT Physics Textbook - Latest Edition for Academic Session 2026-27 (Rationalized Textbook for Class XI and XII, continuing as per NCERT advisory for 2026-27),Topic: Fundamental laws, definitions and applications as per latest NCERT. The section explains governing laws, formulas like μ₀ = 4π.

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CHEMISTRY

Which component of an electromagnetic wave vibrates perpendicular to its direction of propagation?

Electromagnetic waves consist of electric and magnetic fields oscillating perpendicular to each other and to the wave’s direction. This follows from NCERT principle where the relation explains the outcome clearly for students in simple steps.

Ref: NCERT Chemistry Textbook for Class XI and XII, Chapter: Relevant Chemistry topic covering principles and examples as per NCERT.

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Universal Law of Gravitation

Which of the following statements is correct about the gravitational force between two masses?

F = Gm1m2r2 is always attractive, as masses are positive and the force vector points toward each other, making option 1 correct. As per NCERT, applying relevant law/formula with correct units and sign convention leads to It is always attractive. This satisfies dimensional consistency and physical conditions given, so option A is scientifically correct.

Ref: Halliday & Resnick, Fundamentals of Physics, 11th ed., Chapter 13: Gravitation.

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