Question 1

The energy of the first level in an atom is 2.2×10⁻¹⁸ J,and the energy of the second energy level is 1.6×10⁻¹⁸ J.What is the energy of the photon that is emitted if an electron moves from the second level to the first?

Accepted Answer

The energy of the photon emitted is the difference between the two energy levels: 2.2×10⁻¹⁸ J - 1.6×10⁻¹⁸ J = 6.0×10⁻¹⁹ J.

Question 2

What is responsible for binding the electrons to the nucleus?

Accepted Answer

Coulomb force is responsible for binding the electrons to the nucleus. Coulomb force is the force of attraction between opposite charges and the force of repulsion between like charges. In an atom, the negatively charged electrons are attracted to the positively charged nucleus by the Coulomb force, which keeps the electrons in orbit around the nucleus.

Question 3

What does a non-ionized atom always contain?

Accepted Answer

A non-ionized atom always contains the same number of protons and electrons. This is because the number of electrons must equal the number of positive charges in the nucleus so that the atom is neutral overall. The number of neutrons can vary within a given element, but the number of protons (which determines the element itself) cannot change without creating an ion.

Question 4

How can the density of the Sun be measured?

Accepted Answer

The density of the Sun can be measured by using Newton's laws and the Sun's diameter. By determining the mass of the Sun through the gravitational pull it exerts on other celestial bodies, and dividing by the volume of the Sun calculated from its diameter, we can obtain its average density.

Question 5

Which of the following is a set of rules that describes how atoms and subatomic particles behave?

Accepted Answer

Quantum mechanics is the branch of physics that describes the behavior of atoms and subatomic particles, including electrons, protons, and neutrons. It provides a set of mathematical rules, such as the Schrödinger equation, to predict the behavior of particles and their interactions with each other. Kirchhoff's law and the Coulomb force are related to electricity and magnetism, while binding energy refers to the energy required to break apart a nucleus or a molecule.

Question 6

Is it possible for a red star to emit more energy than a blue star?

Accepted Answer

A red star can emit more energy than a blue star if it has a significantly larger surface area, as total energy output depends on both temperature and surface area according to the Stefan-Boltzmann law.

Question 7

The Stefan-Boltzmann law says that hot objects emit energy proportional to the fourth power of their temperature.One star has a temperature of 30,000 K and another star has a temperature of 6,000 K.Compared to the cooler star,how much more energy per second will the hotter star radiate from each square metre of its surface?

Accepted Answer

According to the Stefan-Boltzmann law, the energy radiated per second per unit area, or the radiant flux density, is proportional to the fourth power of the temperature. 
Thus, for the two stars in question, the ratio of their radiant flux densities would be:
$$(\frac{F_1}{F_2}) = (\frac{T_1}{T_2})^4$$
Substituting the temperatures,
$$(\frac{F_1}{F_2}) = (\frac{30,000}{6,000})^4 = 5^4 = 625$$
Thus, the hotter star will radiate 625 times more energy per second from each square metre of its surface compared to the cooler star. 
Therefore, the correct answer is choice C) 625 times.

Question 8

What is the sequence of star colours in order of increasing temperature?

Accepted Answer

The sequence of star colours in order of increasing temperature is red, yellow, blue. This is because the colour of a star is determined by its temperature, with hotter stars emitting bluer light and cooler stars emitting redder light.

Question 9

What is the temperature of an object from which no heat energy can be extracted?

Accepted Answer

This is because at 0 Kelvin, all thermal motion stops and there is no heat energy available to extract. This is also known as absolute zero, the lowest possible temperature.

Question 10

Why does each element have its own set of characteristic absorption lines?

Accepted Answer

Absorption lines are created when the electrons of an element absorb energy and move to a higher energy level. The specific energy levels and transitions available for each element are determined by the unique electron configurations, which result from the number of protons and electrons in the atom. Therefore, each element has its own set of characteristic absorption lines.

Question 11

What has a negative charge and a mass about 1800 times smaller than a proton?

Accepted Answer

A particle with a negative charge and a mass about 1800 times smaller than a proton is an electron. Neutrons are neutral in charge and their mass is almost the same as that of a proton. Molecules and nuclei can have a range of charges and masses, so they do not fit the description given.

Question 12

Which of the following can be determined from the spectrum of a star,without additional information?

Accepted Answer

The rotational velocity of a star can be determined from its spectrum by analyzing the broadening of spectral lines due to the Doppler effect.

Question 13

What is the term for the absorption lines in the visible portion of the spectrum of a star that are produced by hydrogen?

Accepted Answer

The Balmer series consists of the absorption lines in the visible portion of the spectrum of a star that are produced by hydrogen. The Lyman, Paschen, and Brackett series are absorption lines produced by hydrogen in other parts of the electromagnetic spectrum.

Question 14

The Hg line has a wavelength of 434.0 nm when observed in the laboratory.If the Hg line appears in a the spectrum of a star moving away from you,at what wavelength will you observe the line?

Accepted Answer

When the star is moving away from us, it experiences a redshift due to the Doppler effect. This means that the wavelength of the Hg line will increase, causing it to shift towards the red end of the spectrum. Therefore, the wavelength observed will be greater than 434 nm.

Question 15

If you move an electron from a lower energy level to a higher energy level within an atom,how would you describe that atom?

Accepted Answer

When an electron is moved from a lower energy level to a higher energy level within an atom, the atom becomes excited. This means that the electron has absorbed some energy and moved to a higher energy level, but the atom is still neutral and has the same number of protons and electrons.

Question 16

What is the term for atoms that have the same number of protons but a different number of neutrons?

Accepted Answer

Isotopes are atoms that have the same number of protons (and thus the same atomic number) but different numbers of neutrons, resulting in different atomic masses.

Question 17

The Sun emits its maximum intensity of light at about 520 nm.According to Wien's Law,what would the temperature of a star that emits its maximum intensity at 10⁴0 nm be?

Accepted Answer

Wien's Law states that the wavelength of maximum intensity emitted by a body is inversely proportional to its temperature. This can be expressed as λmaxT = constant, where λmax is the wavelength of maximum intensity and T is the temperature.

For the Sun, λmax = 520 nm, so we can write:

520 × 10⁻⁹ m × T = constant

For the star that emits its maximum intensity at 10⁴⁰ nm, we have:

10⁴⁰ × 10⁻⁹ m × T = constant

Dividing the second equation by the first, we get:

(10⁴⁰ × 10⁻⁹ m)/(520 × 10⁻⁹ m) = T

T ≈ 2900 K

Therefore, the temperature of the star that emits its maximum intensity at 10⁴⁰ nm would be approximately 2900 K.

Question 18

A certain spectral line of hydrogen has a wavelength of 410.2 nm when observed in the laboratory.If the same line appears in a star's spectrum at 410.0 nm,what can you conclude about the motion of the star?

Accepted Answer

The difference in wavelength between the laboratory value (410.2 nm) and the star's value (410.0 nm) indicates a shift towards the blue end of the spectrum, known as a blue shift. This means that the star is moving towards the observer.

Question 19

The Sun contains a lot of hot gas,so why do we observe an absorption spectrum rather than an emission spectrum from it?

Accepted Answer

The Sun's photosphere is the outermost layer visible to us, and it has a temperature of around 5,500 degrees Celsius. However, the layers below it, such as the chromosphere and the corona, are hotter. This leads to a situation where the photosphere acts as a cooler "lid" over the hotter layers beneath it. The hot gas in the layers below emits a continuous spectrum, but as it passes through the cooler photosphere, some of the light is absorbed, creating an absorption spectrum.

Question 20

The Sun emits its maximum intensity of light at about 520 nm.According to Wien's Law,at what wavelength would the maximum intensity be for a star with a surface temperature twice that of the Sun?

Accepted Answer

Wien's Law states that the peak wavelength is inversely proportional to the temperature. If the temperature is doubled, the peak wavelength is halved. Therefore, for a star with twice the Sun's temperature, the peak wavelength would be 520 nm / 2 = 260 nm.

Quiz 5: Sun Light and Sun Atoms