MCQ Collection
ECAT Physics MCQs
Practice ECAT Physics questions with answers and explanations.
Choose an option to check your answer.
A.
200
B.
600
C.
800
D.
400
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Correct Answer: D. 400
Explanation:
One half-life reduces the undecayed population by half.
800/2 = 400 nuclei.
Choose an option to check your answer.
A.
Discrete packets of energy
B.
Only continuous mechanical waves
C.
Massive charged particles
D.
Stationary electric fields
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Correct Answer: A. Discrete packets of energy
Explanation:
A photon carries energy proportional to frequency.
The photon model explains effects such as photoelectric emission.
Choose an option to check your answer.
A.
100
B.
50
C.
200
D.
400
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Correct Answer: A. 100
Explanation:
After three half-lives, the remaining fraction is (1/2)^3=1/8.
800/8 = 100 nuclei.
Choose an option to check your answer.
A.
Production of light by heated metals only
B.
Emission of electrons from a surface when light of sufficient frequency falls on it
C.
Deflection of electrons by a magnetic field
D.
Creation of neutrons by visible light
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Correct Answer: B. Emission of electrons from a surface when light of sufficient frequency falls on it
Explanation:
Photoelectric emission requires photon energy above the material's work function.
Increasing intensity mainly increases the number of emitted electrons.
Choose an option to check your answer.
A.
1/2
B.
1/4
C.
1/3
D.
1/8
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Correct Answer: B. 1/4
Explanation:
Twelve hours equals two half-lives.
The remaining fraction is (1/2)^2 = 1/4.
Choose an option to check your answer.
A.
Energy of every electron in the atom
B.
Maximum photon energy
C.
Minimum energy needed to remove an electron from its surface
D.
Energy stored in a capacitor
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Correct Answer: C. Minimum energy needed to remove an electron from its surface
Explanation:
The work function depends on the material and surface condition.
Photoelectric emission begins when photon energy reaches this threshold.
Choose an option to check your answer.
A.
2
B.
4
C.
3
D.
8
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Correct Answer: C. 3
Explanation:
The sequence is 1600, 800, 400, 200.
That is three halvings, so three half-lives.
Choose an option to check your answer.
A.
Particles can never behave like waves
B.
Only photons have momentum
C.
Mass and energy are unrelated
D.
Moving particles have an associated wavelength
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Correct Answer: D. Moving particles have an associated wavelength
Explanation:
Matter waves link momentum with wavelength through λ=h/p.
The effect is important at microscopic scales.
Choose an option to check your answer.
A.
3 × 10^2 J
B.
9 × 10^4 J
C.
3 × 10^14 J
D.
9 × 10^10 J
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Correct Answer: D. 9 × 10^10 J
Explanation:
Use E=mc².
E=1×10^-6×(3×10^8)² = 9×10^10 J.
Choose an option to check your answer.
A.
An allowed discrete energy state of an electron in an atom
B.
Any continuously variable electron energy
C.
The total mass of the atom
D.
The electric charge of the nucleus
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Correct Answer: A. An allowed discrete energy state of an electron in an atom
Explanation:
Bound atomic electrons occupy quantized energy states.
Transitions between levels involve photon absorption or emission.
Choose an option to check your answer.
A.
Atoms with different proton numbers but equal masses
B.
Atoms of the same element with different numbers of neutrons
C.
Ions with different charges only
D.
Molecules with different structures
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Correct Answer: B. Atoms of the same element with different numbers of neutrons
Explanation:
Isotopes have the same atomic number and chemical identity.
Their mass numbers differ because neutron counts differ.
Choose an option to check your answer.
A.
Chemical burning of atoms
B.
Forced ionization by heat only
C.
Spontaneous transformation of unstable nuclei with emission of radiation
D.
Reflection of electromagnetic waves
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Correct Answer: C. Spontaneous transformation of unstable nuclei with emission of radiation
Explanation:
Radioactive decay is a nuclear process.
Its probability is characterized by a decay constant and half-life.