Question 1

The element first found in the Sun's spectrum, then on Earth 30 years later, is

Accepted Answer

Helium was first discovered in the Sun's spectrum before it was found on Earth, hence its name derived from Helios, the Greek god of the Sun.

Question 2

Which of these is emitted when an electron falls from a higher to lower orbital?

Accepted Answer

When an electron falls from a higher to a lower orbital, it emits a photon. This is a fundamental process in quantum mechanics, where the energy difference between the two orbitals is released in the form of electromagnetic radiation, or photons.

Question 3

In Bohr's model of the atom, electrons

Accepted Answer

In Bohr's model, electrons can only occupy certain orbits with specific energies, and they can transition between these orbits, but only in discrete jumps that involve the absorption or emission of a photon. This concept is fundamental to the model and explains the quantized nature of atomic energy levels.

Question 4

What is the name of the temperature scale that places zero at the point where all atomic and molecular motion ceases?

Accepted Answer

The Kelvin scale places zero at absolute zero, the point where all atomic and molecular motion ceases.

Question 5

For hydrogen, the transition from the first to third excited state produces

Accepted Answer

The answer of For hydrogen, the transition from the first...

Question 6

The Sun's observed spectrum is

Accepted Answer

The Sun's spectrum is a continuum because it is a hot body that emits a broad range of wavelengths. The absorption lines, known as Fraunhofer lines, are caused by elements in the Sun's atmosphere absorbing specific wavelengths of light.

Question 7

A jar filled with gas is placed directly in front of a second jar filled with gas. Using a spectroscope to look at one jar through the other you observe dark spectral lines. The jar closest to you contains

Accepted Answer

The dark spectral lines, known as absorption lines, occur when cooler gas in the foreground absorbs specific wavelengths of light emitted by the hotter gas behind it.

Question 8

In a hydrogen atom, a transition from the 2nd to the 1st excited state will produce

Accepted Answer

The transition from the 2nd to the 1st excited state in a hydrogen atom corresponds to the n=3 to n=2 transition, which produces the bright red Balmer alpha (H-alpha) emission line. This is part of the Balmer series observed in the visible spectrum.

Question 9

Electromagnetic radiation

Accepted Answer

Electromagnetic radiation exhibits both wave-like and particle-like properties, a concept central to quantum mechanics. This duality allows it to be described in terms of waves in some situations and as particles (photons) in others.

Question 10

What is true of a blackbody?

Accepted Answer

A blackbody emits radiation with a spectrum that peaks at a wavelength determined by its temperature, according to Wien's displacement law.

Question 11

A frequency of one hundred means the wave is vibrating one hundred million times per second; this is a typical carrier frequency for FM (frequency modulation) radio.

Accepted Answer

A frequency of one hundred million times per second is equivalent to 100 megahertz, which is a typical carrier frequency for FM radio.

Question 12

Increasing the temperature of a blackbody by a factor of 3 will increase its energy by a factor of

Accepted Answer

The energy radiated by a blackbody is proportional to the fourth power of its temperature, according to the Stefan-Boltzmann law. Therefore, if the temperature increases by a factor of 3, the energy increases by $3^4 = 81$.

Question 13

According to the Zeeman effect, the splitting of a sunspot's spectral lines is due to

Accepted Answer

The Zeeman effect refers to the splitting of a spectral line into several components in the presence of a static magnetic field. This phenomenon is observed in sunspots, where strong magnetic fields are present, causing the spectral lines to split accordingly.

Question 14

The observed spectral lines of a star are all shifted towards the red end of the spectrum. Which statement is true?

Accepted Answer

The redshift of spectral lines indicates that the star is moving away from us, which is an example of the Doppler effect. The Doppler effect describes the change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source.

Question 15

If a star was the same size as our Sun, but was 81 times more luminous, it must be

Accepted Answer

The luminosity of a star is proportional to the fourth power of its temperature (L ∝ T^4). If the star is 81 times more luminous, then (T_star/T_sun)^4 = 81, so T_star/T_sun = 3.

Question 16

If a source of light is approaching us at 3,000 km/sec, then all its waves are

Accepted Answer

The Doppler effect causes the wavelength of light from an approaching source to decrease, which is perceived as a shift towards the blue end of the spectrum. The specific percentage shift depends on the relative speed of the source to the speed of light (300,000 km/s). At 3,000 km/s, this is 1% of the speed of light, leading to a 1% blueshift.

Question 17

In the Kelvin scale, absolute zero lies at

Accepted Answer

Absolute zero is the point at which all molecular motion ceases and is defined as 0 K on the Kelvin scale.

Question 18

In general, the spectral lines of molecules are

Accepted Answer

Molecules have more complex spectral lines than atoms because they can undergo not only electronic transitions but also vibrational and rotational transitions, adding to the complexity of their spectra.

Question 19

The total energy radiated by a blackbody depends on

Accepted Answer

The total energy radiated by a blackbody depends on the fourth power of its temperature, as described by the Stefan-Boltzmann law.

Question 20

If the rest wavelength of a certain line is 600 nm, but we observe it at 594 nm, then

Accepted Answer

The answer of If the rest wavelength of a certain...

Quiz 3: Light and Matter: the Inner Workings of the Cosmos