Free Dawn of Modern Physics MCQs with Answers
739 Dawn of Modern Physics MCQs from Physics, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Classical physics cannot explain blackbody radiation and related observations, leading to Planck’s quantum theory, in which energy is emitted or absorbed in discrete packets. Photons provide the particle model of light, with energy and momentum linked to frequency and wavelength, including the photoelectric effect and its threshold frequency.
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Read the Dawn of Modern Physics notesFree MDCAT chapter notes with key terms739 questions · page 26 of 37
- A. Mass
- B. Velocity
- C. Momentum
- D. Both B and C
Explanation: Option D is correct.The wavelength of a moving particle is inversely proportional to its momentum.
Correct answer: Both B and C- A. 1.66 x 10^-8 m
- B. 1.66 x 10^-10 m
- C. 1.66 x 10^-9 m
- D. 1.66 x 10^-12 m
Explanation: Option B is correct.Given data: h=6.63 x10^-34 Js, m=9.1x1 10^-31 kg, q= 1.6x10^-19 J ,V=54 vFind out: λ =?Solution ;Weknow thatλ…
Correct answer: 1.66 x 10^-10 m- A. Copper
- B. Nickle
- C. Aluminium
- D. Silver
Explanation: Option B is correct.Davisson and Germer showed that electrons are diffracted from nickle crystal in exacty same manner as X-rays.
Correct answer: Nickle- A. 10-10 m
- B. 10-20 m
- C. 10-30 m
- D. 10-40 m
Explanation: m = 200g = 0.2kg v = 5m/hr = 5/3600 m/s P = h/λ = mv λ = h/mv = 6.626x10^-34x3600/0.2x5 = 23.85x10^-31 = 2.385x10^-30 = 10^-30m
Correct answer: 10-30 m- A. Particle property
- B. Light property
- C. Wave property
- D. Quantum property
Explanation: Diffracted electron beam from crystal shows wave nature. Davisson Germer experiment showed that electron beams can undergo diffraction…
Correct answer: Wave property- A. 1
- B. 2√ 2
- C. 2
- D. 1√ 2
Explanation: λ = h/√ 2mqV λ∝ 1/√ mq λ p/λ a = √ ma x qa/mp x qp = √ 4mpx 2e/mpx e=√ 8 =2√ 2
Correct answer: 2√ 2- A. 1
- B. √ me/ma
- C. √ 2me/ma
- D. √ me/2ma
Explanation: λ = h/√ 2meV P=√ 2meV Pe/Pa=√ 2meV x eV/2ma(2e)V Pe/Pa=√ me/2ma
Correct answer: √ me/2ma- A. 0.0002nm
- B. 0.002nm
- C. 0.02nm
- D. 0.2nm
Explanation: λ = h/p λ = 6.63x10^-34/3.3x10^-23 =2x10^-11 =0.02x10^-9 m =0.02nm
Correct answer: 0.02nm- A. E1> E3> E2
- B. E1> E2> E3
- C. E2> E3> E1
- D. E1=E2=E3
Explanation: K.E = 1/2. h^2/mλ^2 = h^2/2mλ E∝ 1/m Lesser is the mass, higher is the kinetic energy.
Correct answer: E1> E3> E2- A. 1/2
- B. 2
- C. 1/√ 2
- D. √ 2
Explanation: λ = h/√ 2mKE λ =1/√ KE Thus when KE is doubled, the wavelength is changed by a factor of 1/√2
Correct answer: 1/√ 2- A. λ e,λ p,λ n,λ b
- B. λ e,λ p,λ n,λ a
- C. λ a,λ n,λ p,λe
- D. λ a,λ p,λ n,λ e
Explanation: λ =h/√ 2mE λ ∝ 1/√ m Since m a > m n > m p > m e Therefore, λa, λn, λp, λe is the correct order.
Correct answer: λ a,λ n,λ p,λe- A. Mass
- B. Velocity
- C. Momentum
- D. Charge
Explanation: Wavelength of matter waves is independent of charge.
Correct answer: Charge- A. Interference
- B. Electron diffraction
- C. Polarization
- D. Refraction
Explanation: The experiment shows diffraction of electron through metal crystals.
Correct answer: Electron diffraction- A. Einstein special theory of relativity and quantum mechanics
- B. Maxwell's theory of light
- C. Newtonian mechanic
- D. Huygen's wave theory of light
Explanation: Albert Einstein's groundbreaking work on the special theory of relativity, which introduced concepts like time dilation and the…
Correct answer: Einstein special theory of relativity and quantum mechanics- A. Frame of reference
- B. Inertial frame of reference
- C. Non-inertial frame of reference
- D. None of these
Explanation: A set of coordinate axes with respect to which measurements are made is called a "reference frame" or "coordinate system." The choice of a…
Correct answer: Frame of reference- A. Which moves with uniform velocity on earth
- B. Which is at rest
- C. Which has zero acceleration
- D. All of these
Explanation: For further explanation, view the attached image
Correct answer: All of these- A. Which has zero acceleration
- B. Which has some acceleration
- C. Which is always at rest
- D. None of these
Explanation: A non-inertial frame of reference is a coordinate system or reference frame in which Newton's first law of motion does not hold.
Correct answer: Which has some acceleration- A. Newtonian mechanic
- B. Quantum mechanics
- C. Wave mechanics
- D. None of these
Explanation: Classical physics is based upon Newtonian mechanics, also known as classical mechanics.
Correct answer: Newtonian mechanic- A. Magnetic field
- B. Electric field
- C. Electric and magnetic field
- D. None of these
Explanation: According to Maxwell's theory of electromagnetism, light consists of oscillating electric and magnetic fields that propagate through space…
Correct answer: Electric and magnetic field- A. Newton
- B. Huygen
- C. Faraday
- D. Maxwell
Explanation: The scientist who considered light as an electromagnetic wave and developed the theory of electromagnetism that described light's behavior…
Correct answer: Maxwell