MDCAT ECAT Physics MCQs with Answers – All Units – Page 3

Question 41 Atomic Spectra

What is the ionisation energy of a hydrogen atom in its ground state?

Correct answer C. 13.6 eV

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Question 42 Atomic Spectra

According to Bohr’s model, the angular momentum of an electron in an allowed orbit is ____

Correct answer A. an integral multiple of h/2π

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Question 43 Atomic Spectra

How does the spacing between successive energy levels of hydrogen change as n increases?

Correct answer D. It decreases

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Question 44 Atomic Spectra

The shortest wavelength line in any series of the hydrogen spectrum corresponds to a transition from ____

Correct answer A. n = ∞ to the final level of that series

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Question 45 Atomic Spectra

Why do the dark lines in the absorption spectrum of a gas occur at the same wavelengths as the bright lines in its emission spectrum?

Correct answer A. Both involve the same differences between energy levels

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Question 46 Atomic Spectra

The dark Fraunhofer lines seen in the spectrum of sunlight are caused by ____

Correct answer D. absorption by cooler gases in the Sun's outer atmosphere

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Question 47 Atomic Spectra

What is the energy of the n = 3 level of a hydrogen atom (Eₙ = −13.6/n² eV)?

Correct answer B. −1.51 eV

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Question 48 Atomic Spectra

What energy photon is emitted when an electron in hydrogen falls from n = 3 to n = 2 (Eₙ = −13.6/n² eV)?

Correct answer B. 1.89 eV

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Question 49 Atomic Spectra

The Balmer series of hydrogen lies mainly in which region?

Correct answer A. Visible

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Question 50 Atomic Spectra

The Paschen series of hydrogen lies in which region of the spectrum?

Correct answer B. Infrared

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Question 51 Atomic Spectra

To which energy level do electrons fall to produce the Balmer series?

Correct answer B. n = 2

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Question 52 Atomic Spectra

The lines of the Lyman series are produced when electrons in hydrogen atoms fall to ____

Correct answer A. n = 1

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Question 53 Atomic Spectra

What does the existence of line spectra tell us about electrons in atoms?

Correct answer C. They occupy discrete energy levels

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Question 54 Atomic Spectra

An atom emits a photon when one of its electrons ____

Correct answer D. moves from a higher level to a lower level

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Question 55 Atomic Spectra

What is the energy of an electron in the ground state of a hydrogen atom?

Correct answer B. −13.6 eV

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Question 56 Atomic Spectra

A line emission spectrum is produced by ____

Correct answer C. a hot gas at low pressure

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Question 57 Atomic Spectra

Which source gives a continuous spectrum?

Correct answer B. The glowing filament of a tungsten lamp

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Question 58 Atomic Spectra

How is an absorption line spectrum formed?

Correct answer C. By passing white light through a cool gas

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Question 59 Atomic Spectra

Why can line spectra be used to identify the elements present in a sample?

Correct answer D. Each element has its own unique set of energy levels

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Question 60 Atomic Spectra

In which region of the electromagnetic spectrum does the Lyman series of hydrogen lie?

Correct answer A. Ultraviolet

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