UNIVERSE LECTURE QUESTIONS 4

5. Explain how emission lines and absorption lines are formed. In what sorts of cosmic objects would you expect to see each?

- They are formed when electrons jump to lower energy levels, which then emit high-energy photons. - Produced by a warm cloud of gas. The gas has a low density and is heated which then projects a series of bright emission lines against a black background.

4. Where in an atom would you expect to find electrons? Protons? Neutrons?

An atom is the basic unit of matter I said above it constitutes electrons protons and neutrons. The electrons are negatively charged, protons are positively charged and neutrons are neutral that is no charge. If one looks at the structure of an Atom he finds the neutrons and protons I can find in the central many new region of the atom called the nucleus. While negatively charged electrons room 12 around the nucleus and specific or betts. The actual mass comes from the mass of the nucleus Protons and neutrons are found in the nucleus Neutrons are not found in the nucleus of Hydrogen Electrons are found outside the nucleus orbiting it

22. Explain the results of Rutherford's gold foil experiment and how they changed our model of the atom.

Before the alpha particle scattering experiment performed by Rutherford and his students, the widely excepted model of Atom was JJ Thompson's model of the atom which was that an atom the basic unit of matter consists of a spear of positive charge That is made of protons and in which electrons are in bedded in between. Rutherford after doing the experiment got results which was not consistent with Thompson's model his results were first most of the alpha particles pass through the foil. Second some of them were deflected at acute angles and third only few one in 20,000 got deflected perpendicularly. When he got these results he proposed a new theory which surpasses Thompson's model of the atom. It is the atom contains a nucleus which is composed of protons and neutrons and electrons revolving around the nucleus and orbits. The weight of the Atom is due to the weight of the nucleus, the mass of electrons are negligible in comparison with protons and neutrons. This rejected the Thompson's model of the Atom When Rutherford allowed α particles from a radioactive source to strike a target of gold foil, he found that, although most of them went straight through, some rebounded back in the direction from which they came. (From this experiment, he concluded that the atom must be constructed like a miniature solar system, with the positive charge concentrated in the nucleus and the negative charge orbiting in the large volume around the nucleus.

8. Describe how Bohr's model used the work of Maxwell.

Bow are used the work of Maxwell and propose the following postulates which were provided to be correct later, #1 electrons in the atom orbit the nucleus, #2 the electron can orbit around the nucleus and only certain orbit or distances from the nucleus. These are the energy levels which are also called as the station north stationary orbits and #3 Electrons can jump from lower energy state to higher energy state by absorbing energy and releasing energy when it jumps from higher energy to lower energy state The model states that electrons in atoms move in circular orbits around a central nucleus and can only orbit stably in certain fixed circular orbits at a discrete set of distances from the nucleus. each of the permitted electron orbits around a given atom has a certain energy value; we therefore can think of each orbit as an energy level. To move from one orbit to another (which will have its own specific energy value) requires a change in the electron's energy—a change determined by the difference between the two energy values. If the electron goes to a lower level, the energy difference will be given off; if the electron goes to a higher level, the energy difference must be obtained from somewhere else Maxwell's theory of electromagnetic radiation says that when electrons change either speed or the direction of motion, they must emit energy. Orbiting electrons constantly change their direction of motion, so they should emit a constant stream of energy

18. Explain what dispersion is and how astronomers use this phenomenon to study a star's light. Explain why glass prisms disperse light.

Dispersion is a process in which a ray or a beam of light is passed through the prism and thereby separation of all the constituents color of the white light. The color of light with the highest frequency bands the most and the color of light with the lowest frequency bands a little. The phenomenon of dispersion is used to find the spectrum of the light coming from the stars. The dispersion spectrum is then obtain on the screen and is printed. Every element has its own spectrum. Newton with the help of refraction and dispersion phenomenon of light was able to find solar spectrum. When white light passes through a prism, it is dispersed and forms a continuous spectrum of all the colors.

15. Explain why we have to observe stars and other astronomical objects from above Earth's atmosphere in order to fully learn about their properties.

Due to earth's atmosphere there is a lot of turbulence in air due to various of air mixture, smoke, smog. This disturbance will cause light rays from various stars and planetary bodies suffer a lot of deflection and they do not reach directly to our eyes and their view from earth get disturbed. So to fully understand the properties of stars scientists put telescope at high mountains or in space orbit. One such telescope Hubble Space Telescope is put in earth's orbit which provide better view of planatary objects. It is important to observe the Sun and other astronomical objects in wavelengths other than the visible band of the spectrum. Due to Earth's atmosphere absorbs much of the ultraviolet light coming from space

1. What distinguishes one type of electromagnetic radiation from another?

Electromagnetic radiation with the shortest wavelengths, no longer than 0.01 nanometer, is categorized as gamma rays (1 nanometer = 10-9 meters, Electromagnetic radiation with wavelengths between 0.01 nanometer and 20 nanometers is referred to as X-rays, Radiation intermediate between X-rays and visible light is ultraviolet (meaning higher energy than violet). a. Wavelength, or frequency b. Gamma Rays, x rays, ultra-violet, visible, infrared, microwave, radio

21. Explain how we use spectral absorption and emission lines to determine the composition of a gas.

Every element possesses its own unique omission and absorption spectrum. Like hydrogen which is the major consequence of the universe, have its own absorption and absorption spectrum of which don't match any other elements spectra. If in a mixture there are some gases, one should first obtain absorption or emission spectra of the mixture and then compare that with the spectrum of different gases. And deduce the composition of the mixture Each particular gas can absorb or emit only certain wavelengths of the light peculiar to that gas. It's the precise pattern of wavelengths that makes the signature of each element unique.

11. What are the differences between light waves and sound waves?

First the light belongs to the class electro magnetic waves where is the sound belongs to the mechanical waves. Second light waves don't require a medium for its propagation on the other hand sound waves requires a medium for its propagation. Third speed of light wave is much faster than the speed of sound in any medium further the speed of light and vacuum is the maximum speed of the universe. Fourth light is a transverse wave while the soundwave is longitudinal waves. And fifth like in polarize while sound can't be Light waves → light travels as transverse waves and can travel through a vacuum Sound waves → travels as longitudinal waves and needs to travel through a solid, liquid, or gas; it cannot go through a vacuum

14. Which is more dangerous to living things, gamma rays or X-rays? Explain.

Generally the radiation is like x-rays, gamma rays and UV rays, all are harmful and dangerous as they cause harm to living creatures. Gamma rays is however are more dangerous than x-rays as they are more penetrating that is they Penetrate the body of humans causing carcinogenic transformation of sales lead into cancer and radiation sickness. Gamma rays are high energy ionizing radiations, which leads to higher damage as compared to x rays Gamma rays; gamma rays can carry a lot of energy they can dangerous for our tissues

7. What kind of motion for a star does not produce a Doppler effect? Explain.

If there is a relative motion between the source and the observer there will be a Doppler effect. Hence if the star moves causing a relative motion between the star in the observer, surely there will be a Doppler affect. So the motions like rotational motion and about its axis and linear motion such that the displacement Between the star and the earth don't change, in such cases Doppler affect will not take place. So, in any kind of of motion of star where the relative motion between the star and the observer don't change, there will not be any kind of Doppler affect In any kind of motion of a star where the relative motion between the star and the observer don't change, there will not be any kind of Doppler effect

27. If spectral line wavelengths are changing for objects based on the radial velocities of those objects, how can we deduce which type of atom is responsible for a particular absorption or emission line?

Primarily, the astronomers don't assume presence of an element with mirror a line rather than the whole spectrum is matched with spectrum of elements on earth. Secondly the Doppler affect doesn't change the pattern of lines from a given element rather it ships the whole pattern either towards bluer region or redder region. hence, Doppler affect doesn't oppose the scientists to find the elements, rather it helps to find if the star or other celestial objects move away or closer to the earth It is the precise wavelength (or color) that tells astronomers which lines belong to which element.

10. Explain the difference between radiation as it is used in most everyday language and radiation as it is used in an astronomical context.

Radiation in every day usage is used to denote a stream of particles which is coming out of a radioactive material. The stream of alpha or beta particles from any radio active metal, but you can mutate the cells of the human body and leave them to carcinogenic transformation. In astronomy, the radiation represents a wave which emanates from something and always moves out words. This includes all electromagnetic and mechanical waves. For instance, light is a form of radiation Every day: In everyday language, "radiation" is often used to describe certain kinds of energetic subatomic particles released by radioactive materials in our environment. Astronomical: radiation, as used in this book, is a general term for waves (including light waves) that radiate outward from a source.

16. Explain why hotter objects tend to radiate more energetic photons compared to cooler objects.

Stefan-Boltzmann law States that the energy Flax from a black body at temperature is directly proportional to the fourth power of its absolute temperature this can be mathematically expressed as F which is energy flux equals oh which is a constant equivalent to 5.67×10 to the 8th power Wm to the -2 K to the -4 and is fixed. The photons omitted are due to the return of the electron from the excited state to the ground state. The mid it electronically not have more energy than the Atoms. So, Atoms with higher energy Willamette photons with higher energy as compared to low energy Atoms. It can also be understood by the fact that higher the temperature, higher will be the energy flux. And the higher the energy flux, the higher will the energy of the photon emitted it will be Higher-energy photons correspond to higher-frequency waves (which have a shorter wavelength); lower-energy photons are waves of lower frequency. when electrons go from lower levels to higher ones, they must absorb a photon of just the right energy, and when they go from higher levels to lower ones, they give off a photon of just the right energy.

25. Explain how electrons use light energy to move among energy levels within an atom.

The Atom at room temperature has its electrons in the ground state, but when energy is provided to it, the electrons absorb it and it excites it to an energy level which lasts for millions part of a second which is a process known as excitation. When the electrons absorb it and it excites the electron to a level such that the energy difference between the initial and final portions of the electron corresponds to the frequency of radiation absorbed by the electron. When an electron is present in ground state it has leased energy but when it absorbs energy, it's energy see increases and it reaches an orbit away from the center or nucleus An atom can absorb energy(photons), which raises it to a higher energy level, this causes an electron's movement to a larger orbit and is called excitation.

12. Which type of wave has a longer wavelength: AM radio waves (with frequencies in the kilohertz range) or FM radio waves (with frequencies in the megahertz range)? Explain.

The relation between wavelength and frequency is given by V which is frequency equals C which is the speed of light over an upside down Y which represents the wavelength of the radiation. From this formula it is observed that the wavelength is inversely proportional to the frequency of the radiation. AM radio waves with frequency any kilohertz will have higher wavelength and FM radio waves with frequency and megahertz, as the frequency of FM waves are higher than the a.m. waves. And the frequency is inversely proportional to the wavelength. so, the higher the frequency the lower the wavelength and the lower the frequency the higher the wavelength. AM waves have a longer wave length

23. Is it possible for two different atoms of carbon to have different numbers of neutrons in their nuclei? Explain.

Yes, it is possible for two different Adams of carbon to have different number of neutrons. And both of them are called isotope of carbon. Isotopes differ from one another and only number of neutrons. Here is the number of protons is the same. For an element the number of protons determines its atomic number and periodic table is based on atomic number. So the isotopes belong to the same element. Yes, Atoms with the same number of proton but different numbers of neutrons are defined as Isotopes and there elements remain the same. Think of isotopes as siblings in the same element "family"—closely related but with different characteristics and behaviors.

3. Is your textbook the kind of idealized object (described in section on radiation laws) that absorbs all the radiation falling on it? Explain. How about the black sweater worn by one of your classmates?

A black body is defined as an idealized body which is able to absorb and emit all kinds of radiation in electromagnetic spectrum. The pages in the textbook or white in color and white is the weakest black body, which can absorb radiations. Color white is like wood which cannot have magnetism. It is a poor absorber and emitter of radiations of different wavelengths. Black sweater is the perfect choice in Winters. Black is a color which can absorb Mostly all kinds of radiations of different wavelengths for all time and convert them to heat. Hence the black sweater absorbs all the radiation and converts them into heat provide comfort in Winters A blackbody is an object that does not reflect or scatter any radiation, but absorbs all the electromagnetic energy that falls on it E.g. textbook Black sweater worn by classmate is unlike the blackbody that was described

2. What is a wave? Use the terms wavelength and frequency in your definition.

A wave is defined as the oscillation in space which repeats itself after its wavelength with corresponding frequency, which may be involved with mass and energy transfer from the point of disturbance to a far point which may or may not require a medium to travel upon. Examples are light (electromagnetic wave), sound (mechanical wave) Wave → radiate outward from a source (i.e. radiation) the wavelength is the distance that separates successive wave crests. Frequency is the number of wave cycles that pass per second

9. Explain why light is referred to as electromagnetic radiation.

Light is the resultant of electric and magnetic fields are still eating mutually perpendicular to each other. The direction of propagation of light is perpendicular to both electric and magnetic fields. As the light wave is resultant of interaction of electric and magnetic field's, light is referred to as electromagnetic radiation. And the speed of light and vacuum is equal to 3×10 to the eighth power which is equal to the speed of all electromagnetic radiation in free space. Further it does not require any medium for propagation like electromagnetic radiation and it shows the phenomenon of polarization somewhere to electromagnetic radiations An Electromagnetic wave is caused due to the mutually perpendicular magnetic and electric field

6. Explain how the Doppler effect works for sound waves and give some familiar examples.

The Doppler affect is defined as the fact produced by moving a source of waves in which there is an uplifting shift in frequency for observers, the source is moving towards an downwards shift of frequency from which the source is moving away. The parent or shift of frequency or the wave links caused due to the relative motion of the source with the observer. If the displacement between the source and the observer decreases there is an upward shift in frequency and when the opposite happens there will be a downward shift in the frequency. The best examples are the decrease in frequency of the siren sound of an ambulance went to drives near you. And also a friend of yours calling your name and running towards you there will be a decrease in the frequency The Doppler Effect helps us determine the radial velocity of an object (i.e. its speed toward or away from us) by measuring the wavelengths emitted Doppler Effect is the change of wavelength/frequency due to the motion of the observer and the source of the wave. For example, when a train is moving away, the sound has a lower pitch. We hear the sound change when it's passing by us, first moving toward us and then away from us.

13. Explain why astronomers long ago believed that space must be filled with some kind of substance (the "aether") instead of the vacuum we know it is today.

The electromagnetic waves differed from sound and water waves in a number of ways. The sound waves propagates through the air, water waves require water for the propagation but as the study said, Lake doesn't need any medium for his propagation. This left an impression on the site as of the 19th century which was hard to take. So, the scientist believe that there must be some kind of material which fill space and they called them "aether" Electromagnetic waves do not require water or air: the fields generate each other and so can move through a vacuum (such as outer space). This was such a disturbing idea to nineteenth-century scientists that they actually made up a substance to fill all of space—one for which there was not a single shred of evidence—just so light waves could have something to travel through: they called it the aether.

17. Explain how we can deduce the temperature of a star by determining its color.

The temperature of the star can be found by finding its corresponding color. This is done with the help of Wien's law. If the color of the star is found then its corresponding wavelength is known as its temperature can be found by the following formula called Wien's formula. And upside down Y max which represents the wavelength at which maximum power is emitted = (3x10^8 m/s) / T (in kelvin). amount of energy is radiated. This is because in any solid or denser gas, some molecules or atoms vibrate or move between collisions slower than average and some move faster than average. So when we look at the electromagnetic waves emitted, we find a broad range, or spectrum, of energies and wavelengths. More energy is emitted at the average vibration or motion rate (the highest part of each curve), but if we have a large number of atoms or molecules, some energy will be detected at each wavelength. The separation of different wavelengths of white light through refraction of different amounts

24. What are the three isotopes of hydrogen, and how do they differ?

The three Isotopes of hydrogen are hydrogen (1-1 H), Deuterium (2-1 H) and Tritium (3-1H). The three isotopes of hydrogen differ from one another due to the number of neutrons. Hydrogen has zero neutrons, deuterium has only one neutron, and tritium has only two H1 (Hydrogen 0Neutrons) H2 (deuterium, 1Neutrons) H3 (tritium, 2Neutrons)

26. Explain why astronomers use the term "blueshifted" for objects moving toward us and "redshifted" for objects moving away from us.

When the source (like stars in astronomy) moves towards the observer, there is an apparent upward shift in the frequency that is the frequency of the wave (here, the light) that seems to increase. The highest frequency in the visible spectrum is a violet, So the shift moves towards violet or blue. So the light goes blue, hence, blueshifted. When the source, like stars in astronomy, moves away from the observer, there'll be a downward shift of frequency. The frequency of light seems to be down shifted in frequency. That is the light gets writer. And the lowest frequency in visible spectrum is of red, that's one says red shifted As wavelength gets shorter, they shift toward the blue end of the spectrum: astronomers call this a blueshift. When the wavelength gets longer, we call the change in colors a redshift.

20. Explain what Joseph Fraunhofer discovered about stellar spectra.

in astronomy classification of stars is based on their spectral series electro magnetic radiation from the stars is analyzed by splitting them with the help of a prism or diffraction grading into a spectrum exhibiting a series of colors. This is referred to as stellar spectra. In the year 1802, William Wollaston built an improved spectrometer. With the help of this he found the solar spectrum and soft colors were not uniformly spread but some dark band appeared in between. He mistakenly attributed these bands as natural boundaries between the colors. German physicist Joseph from her for studied the solar spectrum and found about 600 dark lines and rolled out the natural boundary hypothesis. Later researchers found these dark lines are caused due to the absorption of electromagnetic radiation by the gases. So it became clear that some lines go with certain elements Joseph Fraunhofer, discovered that there are more than 600 dark lines, which led scientists to rule out the boundary hypothesis