Lecture 2

Question 1

Nicholas Copernicus

Answer 1

Reintroduced heliocentric system with sun in the centre of the universe
People found it hard to believe Earth was not immovable

Question 2

Johannes Kepler

Answer 2

Heliocentric model works better with elipses

Question 3

3 Laws of Kepler

Answer 3

1) Planets orbit sun in elliptical orbits with Sun at one focus
2) Planets move fastest at perihelion (closer to sun) than at aphelion (far from sun)
3) Orbital period (P) and average distance (a) are related to each other, with const = 1
P^2 = const x a^3

Question 4

Galileo Galilei

Answer 4

Used telescope to observe the Moon and planets, confirm heliocentric system
Discovered Jupiter’s moons (Io, Europa, Ganymede, Callisto)
Discovered phases of Venus

Question 5

Isaac Newton

Answer 5

Used theory of gravity to explain planetary motions

Question 6

Newton’s 3 Laws of Motion

Answer 6

1) Object moves at constant velocity unless a net force acts to change its speed or direction
2) F = m x a
3) For any force, there is always an equal and opposite reaction force

Question 7

Newton’s Law of Gravity

Answer 7

Fg = [G(M1M2])/d^2

Strength of gravitation attraction between two objects

Question 8

Einstein’s Law of Gravity

Answer 8

“General Relativity”
Mass of sun causes spacetime to curve
Planets and comets follow straightest possible path allowed by this curvature

Question 9

Kinetic energy
Potential energy
Radiative energy

Answer 9

Kinetic: Due to motion
Potential: Stored
Radiative: Electromagnetic radiation (waves/photons)

Question 10

Parts of atom

Answer 10

Nucleus: Protons and neutrons
Cloud: Electrons

Question 11

Isotopes
Neutral atom
Ionized atom

Answer 11

Isotopes: +/- neutrons, heavier or lighter atoms

Neutral: # of protons and electrons are same

Ionized: 1 or more electrons missing

Question 12

How to calculate # of neutrons

Answer 12

Atomic mass - Protons

Question 13

How are atoms held together in each phase?

Answer 13

(From weak to strong electromagnetic attraction)
Plasma
Gas
Liquid
Solid

Question 14

Wien’s Law

Answer 14

Every object warmer than 0 K emits thermal radiation w/ a CONTINUOUS SPECTRUM
All thermal radiators emit light w/ same distinct shape to their distribution of intensity vs colour (blackbody radiation curve)

“The colour (wavelength) where a thermal emitter is brightest is directly proportional to the material’s temp”

Question 15

Properties of thermal radiation

Answer 15

1) Hotter objects emit more light at all freqs
2) Hotter objects emit more photons w/ higher avg energy
3) Peak wavelength is given by Wien’e Law: wavelength(max) = 2.9x10^6/T

Question 16

Absorption line spectrum

Emission line spectrum

Answer 16

Absorption: View light coming from continuous spectrum source passing thru gas

Emission: This gas viewed against dark background and its atoms are excited, we see it coming from the gas

Question 17

Speed of light (electromagnetic radiation)

Answer 17

c = 300,000 km/s

Question 18

Name the planets in order from closest to sun to furthest

Answer 18

Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto

Question 19

Parsec

Answer 19

Distance corresponding to parallax angle of one arc-second