Unit 7

X-Rays and Radioactivity Radioactivity Radioactivity is the process of nuclear decay (radioactive decay). When unstable nuclei lose energy. Nothing new in the environment; it’s been going on since time zero. It warms Earth’s interior, is in the air we breathe, and is present in all rocks (some in trace amounts). It is natural.

The radioactive decay of nature’s elements occurs in the A.soil we walk on. B.air we breathe. C.interior of Earth. D.All of the above. X-Rays and Radioactivity CHECK YOUR NEIGHBOR

The radioactive decay of nature’s elements occurs in the A.soil we walk on. B.air we breathe. C.interior of Earth. D.All of the above. X-Rays and Radioactivity CHECK YOUR ANSWER

Alpha, Beta, and Gamma Rays Radioactive elements emit three distinct types of radiation:  —alpha: positively charged (helium nuclei)  — beta: negatively charged (electrons)  —gamma (electromagnetic radiation)

Alpha, Beta, and Gamma Rays Relative penetrations

The origins of radioactivity go back to A.military activities in the mid-20th century. B.the Industrial Revolution two centuries ago. C.the beginning of human error. D.before humans emerged on Earth. Alpha, Beta, and Gamma Rays CHECK YOUR NEIGHBOR

The origins of radioactivity go back to A.military activities in the mid-20th century. B.the Industrial Revolution two centuries ago. C.the beginning of human error. D.before humans emerged on Earth. Alpha, Beta, and Gamma Rays CHECK YOUR ANSWER

Any atom that emits an alpha particle or beta particle A.becomes an atom of a different element, always. B.may become an atom of a different element. C.becomes a different isotope of the same element. D.increases its mass. Alpha, Beta, and Gamma Rays CHECK YOUR NEIGHBOR

Any atom that emits an alpha particle or beta particle A.becomes an atom of a different element, always. B.may become an atom of a different element. C.becomes a different isotope of the same element. D.increases its mass. Explanation: Contrary to the failures of alchemists of old to change elements from one to another, this was going on all around them—unnoticed. Alpha, Beta, and Gamma Rays CHECK YOUR ANSWER

Alpha, Beta, and Gamma Rays Food irradiation kills microbes. Doesn’t make the food radioactive. There is no diarrhea with astronauts in space (their food is first irradiated).

How are you exposed to radiation Sun Minerals in Earth Concrete/brick Power plants Medicine Smoking

Which of these is the nucleus of the helium atom? A.Alpha B.Beta C.Gamma D.All are different forms of helium. Alpha, Beta, and Gamma Rays CHECK YOUR NEIGHBOR

Which of these is the nucleus of the helium atom? A.Alpha B.Beta C.Gamma D.All are different forms of helium. Alpha, Beta, and Gamma Rays CHECK YOUR ANSWER

Which of these is actually a high-speed electron? A.Alpha B.Beta C.Gamma D.All are high speed. Alpha, Beta, and Gamma Rays CHECK YOUR NEIGHBOR

Which of these is actually a high-speed electron? A.Alpha B.Beta C.Gamma D.All are high speed. Explanation: Choice D may be true, but doesn’t directly answer the question. Bending Light nvisible&view=detail&mid=7F C4F290AE42F7F C 4F290AE42F&FORM=VIRE Alpha, Beta, and Gamma Rays CHECK YOUR ANSWER

Homework- Unit 7 Research the benefits and disadvantages of Nuclear Power Plants. List at least 5 for each category. (10 pts) Research on Nuclear Power plant disaster. – Include the date, time (if possible) and place of the disaster – List the important people involved in the disaster – Explain what went wrong with the Power Plant to cause the disaster. – Explain what measures one could have taken to save the Power plant – Finally summarize your findings from the research above into a paragraph. (10 pts)

Radioactive Half-Life The rate of decay for a radioactive isotope is measured in terms of a characteristic time, the half-life, the time for half of an original quantity of an element to decay.

Radioactive Half-Life Uranium-238 to lead-206 through a series of alpha and beta decays. In 4.5 billion years, half the uranium presently in Earth will be lead.

A certain isotope has a half-life of 10 years. This means the amount of that isotope remaining at the end of 10 years will be A.zero. B.one-quarter. C.half. D.the same. Radioactive Half-Life CHECK YOUR NEIGHBOR

A certain isotope has a half-life of 10 years. This means the amount of that isotope remaining at the end of 10 years will be A.zero. B.one-quarter. C.half. D.the same. Radioactive Half-Life CHECK YOUR ANSWER

Suppose the number of neutrons in a reactor that is starting up doubles each minute, reaching 1 billion neutrons in 10 minutes. When did the number of neutrons reach half a billion? A.1 minute B.2 minutes C.5 minutes D.9 minutes Radioactive Half-Life A challenge…

Suppose the number of neutrons in a reactor that is starting up doubles each minute, reaching 1 billion neutrons in 10 minutes. When did the number of neutrons reach half a billion? A.1 minute B.2 minutes C.5 minutes D.9 minutes Explanation: This question would be appropriate with Appendix D, Exponential Growth and Doubling Time. Can you see that working backward, each minute has half the number of neutrons? Radioactive Half-life CHECK YOUR ANSWER

Geiger counter detects incoming radiation by a short pulse of current triggered when radiation ionizes a gas in the tube. Scintillation counter indicates incoming radiation by flashes of light produced when charged particles or gamma rays pass through the counter. Radiation Detectors

Radiometric Dating Carbon-14 is a beta emitter and decays back to nitrogen. Because living plants take in carbon dioxide, any C-14 lost by decay is immediately replenished with fresh C-14 from the atmosphere. Dead plants continue emitting C-14 without replenishment.

Radiometric Dating Relative amounts of C-12 to C-14 enable dating of organic materials.

The half-life of carbon-14 is about 5730 years, which means that the present amount in your bones will reduce to zero A.when you die. B.in about 5730 years. C.in about twice 5730 years. D.None of the above. Radiometric Dating CHECK YOUR NEIGHBOR

The half-life of carbon-14 is about 5730 years, which means that the present amount in your bones will reduce to zero A.when you die. B.in about 5730 years. C.in about twice 5730 years. D.None of the above. Explanation: In theory, the amount never reaches zero. In eons to come, trace amounts of the carbon-14 in your bones, even if completely dissolved, will still exist. Radiometric Dating CHECK YOUR ANSWER

“Lab Day” 1.Practice Nuclear Reactions WS 2.Lecture Nuclear Power (all on board)-get new HW 3. how it works: &mid=3A72CE89670CE694019C3A72CE89670CE694019C&FORM=VRDGAR Chernobyl Ap Ukraine : detail&mid=DA8C1C585A543D0154FBDA8C1C585A543D0154FB&FORM=VIRE &mid=3A72CE89670CE694019C3A72CE89670CE694019C&FORM=VRDGAR detail&mid=DA8C1C585A543D0154FBDA8C1C585A543D0154FB&FORM=VIRE

Homework- Unit 8- 5 pts 1.Go to the following website: explained.info/index.htm#.Vvrf9dH5P5phttp:// explained.info/index.htm#.Vvrf9dH5P5p 2.Click on “The Basics” for the E=mc2 equation. 1.Explain what each letter stands for AND what the units are for each letter. 2.Explain how coal powered trains work (look under energy). 3.Read the first paragraph under “what does the equation mean” and explain what is means. 4.Listen to Einstein explain his theory. 3.Click on “ Solving the Equation” 1.Write down the example Provided. 2.What is the conclusion that one can draw from reading the bottom of the page.

Nuclear Power Movie Three mile Island: zvjI (44 minutes) March 28, zvjI Make sure HW was given

Unit 8

Video clips General relativity: in%27s+theory+of+relativity&adlt=strict&view =detail&mid=E2EE5E3E3FC0A36C2FE2E2EE5E 3E3FC0A36C2FE2&FORM=VRDGAR in%27s+theory+of+relativity&adlt=strict&view =detail&mid=E2EE5E3E3FC0A36C2FE2E2EE5E 3E3FC0A36C2FE2&FORM=VRDGAR gravitational-waves-discovery-explained-by- experts-video.html gravitational-waves-discovery-explained-by- experts-video.html

Motion is Relative The place from which motion is observed and measured is a frame of reference. – An object may have different velocities relative to different frames of reference. To measure the speed of an object, we first choose a frame of reference and pretend that we are in that frame of reference standing still. – Then we measure the speed with which the object moves relative to us—that is, relative to the frame of reference. Isn’t there some reference frame that is still? Isn’t space itself still, and can’t measurements be made relative to still space?

Theory of Relativity Special General

Special (a) An observer moving with the spaceship observes the light flash moving vertically between the mirrors of the light clock. (b) An observer who sees the moving ship pass by observes the flash moving along a diagonal path.

Spacetime Space and time are intimately linked together. Things exist in spacetime. – Each object, each person, each planet, each star, each galaxy exists in what physicists call “the spacetime continuum.” One observer’s measurements of space and time differ from the measurements of another observer in some other realm of spacetime in such a way that each observer will always measure the same ratio of space and time for light: the greater the measured distance in space, the greater the measured interval of time.

Bending of Light by Gravity According to the principle of equivalence, if light is deflected by acceleration, it must be deflected by gravity. How so? Einstein’s answer: Light is massless, but it’s not “energyless.” – Gravity pulls on the energy of light because energy is equivalent to mass. The trajectory of a flashlight beam is identical to the trajectory of a baseball “thrown” at the speed of light. – Both paths curve equally in a uniform gravitational field.

We learned previously that the pull of gravity is an interaction between masses. And we learned that light has no mass. Now we say that light can be bent by gravity. Isn’t this a contradiction? A.Yes, it is a contradiction. B.No, it is not a contradiction. C.It is a contradiction only if the light is red in color. D.It is a contradiction only if the light is blue in color. Bending of Light by Gravity CHECK YOUR NEIGHBOR

We learned previously that the pull of gravity is an interaction between masses. And we learned that light has no mass. Now we say that light can be bent by gravity. Isn’t this a contradiction? A. Yes, it is a contradiction. B.No, it is not a contradiction. C.It is a contradiction only if the light is red in color. D.It is a contradiction only if the light is blue in color. Explanation: There is no contradiction when the mass–energy equivalence is understood. The fact that gravity deflects light is evidence that gravity pulls on the energy of light, which is equivalent to mass! Bending of Light by Gravity CHECK YOUR ANSWER

Why do we not notice the bending of light in our everyday environment? A.Bending of light never occurs anywhere; it is only a theory. B.Bending of light does not occur in our everyday environment; it only occurs in outer space. C.There is bending, but it is very minute and not perceptible to us. D.None of the above. Bending of Light by Gravity CHECK YOUR NEIGHBOR

Why do we not notice the bending of light in our everyday environment? A.Bending of light never occurs anywhere; it is only a theory. B.Bending of light does not occur in our everyday environment; it only occurs in outer space. C.There is bending, but it is very minute and not perceptible to us. D.None of the above. Explanation: Only because light travels so fast; just as, over a short distance, we do not notice the curved path of a high-speed bullet, we do not notice the curving of a light beam. Bending of Light by Gravity CHECK YOUR ANSWER

Gravity, Space, and a New Geometry General relativity calls for a new geometry: Space is a flexible medium that can bend and twist. The presence of mass produces the curvature, or warping, of spacetime. Masses respond in their motion to the warping of the spacetime they inhabit. Spacetime near a star is curved in a way similar to the surface of a waterbed when a heavy ball rests on it

E=mc 2

Theory of Relativity Movies 51I (50 min) 51I HjjX4 (75 min) HjjX4