MDCAT ECAT Physics MCQs with Answers – All Units – Page 2

Question 21 Nuclear Physics

Radioactive decay is spontaneous. Which statement follows from this?

Correct answer C. The decay rate is unaffected by temperature, pressure or chemical state

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Question 22 Nuclear Physics

An alpha particle is identical to ____

Correct answer D. a helium nucleus

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Question 23 Nuclear Physics

In beta-minus decay, the emitted electron comes from ____

Correct answer A. a neutron in the nucleus changing into a proton

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Question 24 Nuclear Physics

Which statement about gamma radiation is correct?

Correct answer C. It is electromagnetic radiation with no charge

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Question 25 Nuclear Physics

Which type of nuclear radiation produces the most ionisation per unit length of its path?

Correct answer C. Alpha particles

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Question 26 Nuclear Physics

When a nucleus emits an alpha particle, its ____

Correct answer B. mass number falls by 4 and atomic number by 2

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Question 27 Atomic Spectra

What is the ratio of the wavelength of the first Lyman line (n = 2 to 1) to that of the first Balmer line (n = 3 to 2)?

Correct answer B. 0.185

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Question 28 Atomic Spectra

What is the angular momentum of an electron in the second Bohr orbit of hydrogen (h = 6.63 × 10⁻³⁴ J s)?

Correct answer C. 2.11 × 10⁻³⁴ J s

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Question 29 Atomic Spectra

What is the wavelength of the first line of the Lyman series (n = 2 to n = 1) (R = 1.097 × 10⁷ m⁻¹)?

Correct answer A. 122 nm

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Question 30 Nuclear Physics

Which particles are found inside the nucleus of an atom?

Correct answer D. Protons and neutrons

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Question 31 Nuclear Physics

The mass number A of a nucleus is equal to ____

Correct answer D. the total number of protons and neutrons

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Question 32 Nuclear Physics

Isotopes of an element have ____

Correct answer D. the same number of protons but different numbers of neutrons

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Question 33 Nuclear Physics

Radioactive decay is described as random. What does this mean?

Correct answer B. It is impossible to predict which nucleus will decay next

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Question 34 Atomic Spectra

Using the Rydberg formula, what is the wavelength of the first Balmer line (n = 3 to n = 2) (R = 1.097 × 10⁷ m⁻¹)?

Correct answer D. 656 nm

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Question 35 Atomic Spectra

What is the wavelength of the series limit of the Lyman series (R = 1.097 × 10⁷ m⁻¹)?

Correct answer D. 91.2 nm

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Question 36 Atomic Spectra

What is the wavelength of the series limit of the Balmer series (R = 1.097 × 10⁷ m⁻¹)?

Correct answer B. 365 nm

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Question 37 Atomic Spectra

Hydrogen atoms are excited to the n = 4 level. How many different spectral lines can be emitted as they return to the ground state?

Correct answer B. 6

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Question 38 Atomic Spectra

How much energy is needed to ionise a hydrogen atom whose electron is in the n = 2 level (Eₙ = −13.6/n² eV)?

Correct answer D. 3.4 eV

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Question 39 Atomic Spectra

What is the minimum energy needed to raise a hydrogen atom from its ground state to its first excited state (Eₙ = −13.6/n² eV)?

Correct answer A. 10.2 eV

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Question 40 Atomic Spectra

The radius of the first Bohr orbit of hydrogen is 0.053 nm. What is the radius of the third orbit (rₙ = n²r₁)?

Correct answer D. 0.477 nm

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