@?physics

Flashcards 2022-02-10 Where is all radiation emitted from?? An unstable nucleus. What are the four different types of radiation?? Alpha Beta-minus Beta-plus Gamma What particle is emitted in beta-minus radiation?? An electron. What particle is emitted in beta-plus radiation?? A positron. What instrument do you use to detect radiation?? A Geiger-Muller counter. What must you subtract from every Geiger-Muller counter in order to accurately determine the radioactivity of a substance?? The background radiation.

Flashcards 2022-02-08 Where does the definition for $1 \text{au}$ come from?? The average earth-to-sun distance. What does the definition for $1 \text{ly}$ come from?? It’s the speed light travels per year in a vacuum. What’s “parsec” short for?? “parallax arcsecond” What is $1$ degree in arcminutes (READ)?? $$ 60 \text{arcminutes} $$ What is $1$ arcminutes in arcseconds (READ)?? $$ 60 \text{arcseconds} $$ What is $1$ degree in arcseconds (READ)?? $$ 3600 \text{arcseconds} $$ What is the notation for one arcminute?

Flashcards 2022-02-07 What are the two types of beta decay?? Beta minus Beta plus How should you write an electron in a beta decay equation?? $$ _{-1}^0 e $$ When denoting particles in a beta decay equation, such as $_y^x \alpha$, what does $y$ represent?? The charge. When denoting particles in a beta decay equation, such as $_y^x \alpha$, what does $x$ represent?? The nucleon number. What two quantities are conserved in a beta decay equation?

Flashcards 2022-01-31 What are the four fundamental forces?? Strong nuclear force Weak nuclear force Electromagnetic force Gravitational force In what context does the strong nuclear force show up?? Holding nucleons together. When does the electromagnetic force act?? When two charged objects interact. In what context does the weak nuclear force show up?? Beta decay. When does the gravitational force show?? When any particles have mass. What is the relative strength of the strong nuclear force?

Flashcards 2022-01-26 What simplifying model do we use when talking about emitters and absorbers of electromagnetic radiation?? Black bodies. What two main assumptions are made about a black body?? They are perfect emitters and absorbers of electromagnetic radiation They emit radiation at all wavelengths Why is the sun yellow if it can be modelled as a near-perfect black body?? Because it is hotter than its surroundings and so is glowing. What is special about how a black body emits radiation at all wavelengths?

Flashcards 2022-01-25 What is this?? A Hertzsprung-Russell diagram. What is on the $x$-axis of a Hertzsprung-Russell diagram?? Temperature. Which out of luminosity and temperature goes in the wrong direction on a Hertzsprung-Russell diagram?? Temperature. What is on the $y$-axis of a Hertzsprung-Russell diagram?? Luminosity. What is sometimes confusing about the temperature values on a Hertzsprung-Russell diagram?? They measure “effective temperature”, not the temperature of the core. What are the units for luminosity measured on a Hertzsprung-Russell diagram?

Flashcards 2022-01-20 What did J. J. Thomson discover in 1897?? The electron. What model did J. J. Thomson propose for the atom?? The plum pudding model. What is the plum pudding model?? The idea that an atom contains negative electrons embedded in a uniform sea of positive charge. What is the one-sentence summary of the alpha-scattering experiment?? Fire alpha particles at a thin gold film and see where the alpha particles are deflected to using a microscope.

Flashcards 2022-01-18 What are the four characteristics of a planet (ORFC)?? It is in __O__rbit around a star It has a mass large enough that gravity makes it __R__ound It has no __F__usion reactions It has __C__leared its orbit of most other objects What is the difference between a planet and a dwarf planet?? A dwarf planet has not cleared its neighbourhood. What is an asteroid?? An small, uneven and un-icy object that orbits the sun.

Flashcards 2022-01-18 What is the first stage in the evolution of a star?? A nebula. What is the main element in a nebula?? Hydrogen. What happens to a nebula after a long period of time?? It collapses under its own gravity. As a nebula is collapsing under its own gravity, what happens to the stores of energy?? The gravitational potential potential is transfered to kinetic energy. What happens as the gravitational energy of the dust particles in a nebula is transferred to kinetic energy?

Flashcards 2021-12-08 What is gravitational potential?? The energy transferred per unit mass to move an object from infinity to a point. What is the gravitational potential at infinity?? $$ 0\text{J}\text{kg}^{-1} $$ Why is gravitational potential always negative?? Because you’re having to do the opposite of what gravity wants you to do. What is gravitational potential energy?? The energy transferred to move an object from infinity to a point. What does the graph of $V$ against $r$ look like for gravitational potential?

Flashcards 2021-12-06 What speed must a satellite be going at to orbit a planet at radius $r$?? $$ \sqrt{\frac{GM}{r}} $$ What three things must be true for a geostationary satellite?? It must be in an orbit above the Earth’s equator. It must rotate in the same direction as the Earth’s rotation. It must have an orbital period of 24 hours. What is true about a polar orbit?? It passes over a planet’s poles.

Flashcards 2021-12-01 What do Kepler’s laws describe?? The motion of orbits. What is Kepler’s First Law?? All of the planets move in elliptical orbits with the sun at one focus. What is Kepler’s Second Law?? The radius vector sweeps out equal areas in equal times. What is the “radius vector” for Kepler’s Second Law?? The imaginary line between the sun and the planet. Which of Kepler’s laws does this show?? Kepler’s second law. What is Kepler’s Third Law?