Andrew Rex - Commonly asked questions in physcis

1 Classical Mechanics 1
1-What Is Physics? 1
2-What Is the SI System of Units? 2
3-How Are SI Units Defined? 2
4-What Are SI Base Units and Derived Units? 3
5-Are SI Units the Only Ones Used in Physics? 4
6-What Are Velocity and Acceleration? 4
7-Are Velocity and Speed the Same? 6
8-What Is a Force? 8
9-What Are Newton’s Laws of Motion? 8
10-Are Mass and Weight the Same? 9
11-Why Do Different Masses (or Weights) Fall at the Same Rate? 10
12-What Are Friction and Drag Forces? 10
13-What Are Work and Energy? 11
14-What Is the Work–Energy Theorem? 12
15-What Is Potential Energy? 12
16-What Is Conservation of Mechanical Energy? 12
17-What Is Power? 13
18-What Is Momentum Conservation? 13
19-How Do Rockets Work? 14
20-What Is Center of Mass? 14
21-What Is Simple Harmonic Motion? 15
22-What Are Torque and Angular Momentum? 17
23-What Is a Gyroscope? 18
24-What Is Newton’s Law of Universal Gravitation? 19
25-Why Is Newton’s Gravitation Law Considered “Universal”? 19
26-What Keeps Planets and Satellites in Orbit? 20
27-What Orbits Do the Planets Follow? 21
28-What Other Kinds of Orbital Paths Are Possible? 21
29-What Is a Geosynchronous Satellite? 21
30-Why Does the Acceleration due to Gravity Vary with Altitude and
Latitude? 22
31-What Is the Coriolis Force? 23
32-Can Classical Mechanics Explain Everything? 23

2 Electromagnetism and Electronics 25
33-What Are Electric Charges, and How Do They Affect Each Other? 25
34-Why Do I Get Shocked after Walking on Carpet? 26
35-What Is Coulomb’s Law? 26
36-How Strong Is the Electric Force Compared with Gravity? 26
37-What Is Quantization of Charge? 27
38-What Is an Electric Field? 27
39-What Happens in a Thunderstorm? 28
40-What Is Electric Potential? 29
41-What Is a Capacitor? 29
42-How Does a Defibrillator Work? 30
43-What Are Electric Current and Resistance? 30
44-What Is Ohm’s Law? 31
45-What Are Semiconductors? 32
46-What Are Diodes and Transistors? 33
47-What Are Superconductors? 35
48-What Are Some Applications of Superconductors? 36
49-What Are Magnetic Dipoles and Magnetic Fields? 36
50-What about Earth’s Magnetic Field? 38
51-How Do Animals Use Earth’s Magnetic Field? 39
52-What Is Electromagnetism? 39
53-What Is Magnetic Induction? 39
54-How Does an Electromagnet Work? 40
55-What Is a Solenoid? 41
56-How Are Magnetic Materials like Electromagnets? 42
57-What Are Direct Current and Alternating Current? 43
58-How Do Electric Motors Work? 44
59-What Is an Electromagnetic Wave? 45
60-What Is the Electromagnetic Spectrum? 46
61-How Does Wireless Communication Work? 47
62-How Does a Microwave Oven Work? 48

3 Solids and Fluids 49
63-What Are the States of Matter? 49
64-What Is Plasma? 50
65-How Are the States of Matter Related to Density, Pressure, and
Temperature? 50
66-What Makes Some Solids Stronger Than Others? 51
67-What Is a Fluid? 52
68-Why Does Fluid Pressure Depend on Depth? 52
69-How Does a Barometer Work? 54
70-What Is Decompression Sickness? 54
71-How Is Air Pressure Related to Weather? 55
72-What Does Your Blood Pressure Mean? 56
73-What Causes Buoyancy? 56
74-What Is Bernoulli’s Principle? 57
75-What Is Surface Tension? 58
76-What Is a Superfluid? 60
77-What Are Transverse and Longitudinal Waves? 61
78-What Is Wave Interference? 62
79-What Is a Standing Wave? 62
80-What Is a Tsunami (Tidal Wave)? 63
81-How Is Sound Generated? 64
82-What Is the Speed of Sound? 64
83-What Is the Decibel Scale? 65
84-How Does Your Hearing Work? 65
85-How Are Music and Musical Harmonies Made? 67
86-What Is the Doppler Effect? 68
87-What Makes a Sonic Boom? 69

4 Quantum Mechanics 71
88-What Is Quantization? 71
89-How Are Mass and Electric Charge Quantized? 72
90-How Is Atomic Energy Quantized? 73
91-What Is Blackbody Radiation? 74
92-How Is Electromagnetic Radiation Quantized? 76
93-What Is a Photon? 76
94-What Is the Photoelectric Effect? 77
95-What Is Wave–Particle Duality? 80
96-What Does the Two-Slit Experiment Reveal about Wave–Particle
Duality? 80
97-What Are Particle Waves? 82
98-What Is the Heisenberg Uncertainty Principle? 83
99-What Does Quantum Mechanics Tell Us about Hydrogen Atoms? 84
100-How Does Quantum Mechanics Describe Transitions between States? 87
101-How Does Quantum Mechanics Apply to Other Atoms? 87
102-What Is the Zeeman Effect? 90
103-What Is the Stern–Gerlach Experiment? 91
104-What Are NMR and MRI? 91
105-What Is Quantum Tunneling? 91
106-What Is a Quantum Computer? 92
107-What Are Some Other Applications of Quantum Mechanics? 92

5 Light and Optics 95
108-What Is Light? 95
109-What Are Ray Optics and Wave Optics? 96
110-What Is the Law of Reflection? 96
111-How Does the Law of Reflection Explain the Images You See in
a Mirror? 97
112-Why Doesn’t Everything Reflect like a Mirror? 97
113-How Do Curved Mirrors Form Images? 97
114-What Is Refraction? 99
115-What Is Total Internal Reflection, and How Is It Used? 101
116-What Is Dispersion? 101
117-Why Do Diamonds Sparkle? 102
118-How Do Rainbows Form? 102
119-How Do Lenses Work? 103
120-How Do Converging Lenses Form Images? 105
121-Does Your Eye Form Images This Way? 106
122-What Are Aberration Effects in Lenses? 106
123-What Are Some Common Refractive Vision Disorders, and How Are They
Corrected with Lenses? 106
124-What Does Your Corrective Lens Prescription Mean? 107
125-How Do Microscopes Work? 108
126-What Is an Electron Microscope? 109
127-How Do Telescopes Work? 109
128-How Does a Refracting Telescope Work? 110
129-How Does a Reflecting Telescope Work? 111
130-What Are Some Novel Designs for Modern Reflecting Telescopes? 113
131-Can You Use Telescopes to See Other Kinds of (Invisible) Radiation? 113
132-How Does Interference Reveal Light’s Wave Properties? 114
133-Can You See Thin-Film Interference from White Light? 114
134-Are There Any Useful Applications of Interference? 116
135-What Is Diffraction? 117
136-What Is Polarization, and Why Is It Useful? 117
137-Why Is the Sky Blue? 118
138-How Do Lasers Work, and What Makes Them Different from Other Light
Sources? 118
139-How Do CD and DVD Players Work? 119
140-What Is a Light-Emitting Diode? 119
141-What Is a Solar (Photovoltaic) Cell? 120

6 Thermodynamics 121
142-What Is Temperature? 121
143-What Are Some Common Temperature Scales? 122
144-What Is the Kinetic Theory of Gases? 123
145-What Is Thermal Expansion? 125
146-What Are the Units for Thermal Energy, Heat, and Food Energy? 127
147-What Are Heat Capacity and Specific Heat? 128
148-How Is Specific Heat Measured for Gases? 128
149-What Is the Equipartition Theorem? 129
150-What Are Phase Changes? 130
151-What Is Latent Heat? 131
152-What Is Evaporative Cooling? 131
153-What Is the First Law of Thermodynamics? 131
154-What Are Conduction, Convection, and Radiation? 132
155-How Does a Thermos Bottle Work? 133
156-What Is the Greenhouse Effect? 133
157-What Is the Second Law of Thermodynamics? 134
158-What Is Entropy? 135
159-What Is a Heat Engine? 137
160-How Do Refrigerators, Air Conditioners, and Heat Pumps Work? 138
161-What Is a Fuel Cell? 138
162-What Are Quantum Statistics? 139
163-How Cold Can You Get? 140

7 Atoms and Nuclei 143
164-Atoms and Elements—What Are They? 143
165-What Are Atomic Spectra? 144
166-What Is the Rutherford–Bohr Model of the Atom? 144
167-What Are Atomic Orbitals and Shells? 148
168-How Do Atomic Shells and Subshells Explain the Periodic Table? 149
169-How Are X-Rays Produced? 150
170-What Is the Difference between Characteristic and Bremsstrahlung
X-Rays? 151
171-How Do Medical X-Rays Work? 152
172-What Are the Basic Properties of Nuclei? 153
173-What Is the Strong (Nuclear) Force? 153
174-How Are Nuclei Bound by the Nuclear Force? 155
175-Which Combinations of Z and N Are More Stable? 155
176-What Is Nuclear Binding Energy? 156
177-What Are the Benefits and Dangers of Radioactive Nuclei? 156
178-What Is Alpha Decay? 156
179-What Is Beta Decay? 158
180-What Is Gamma Decay? 159
181-What Is a Radioactive Half-Life? 160
182-What Are Decay Chains? 160
183-How Are Radioactive Nuclides Used in Medicine? 161
184-How Does Radioactive Dating Work? 162
185-What Is Fission? 163
186-What Is a Chain Reaction? 164
187-What Makes an Atomic Bomb Work? 165
188-How Much Energy Is Released in Fission? 165
189-How Does a Nuclear Reactor Work? 165
190-What Is Fusion? 168
191-What Is a Hydrogen Bomb? 169
192-What Are the Prospects for Large-Scale Energy Production from
Fusion? 169

8 Fundamental Particles and Forces 171
193-What Are Fundamental and Composite Particles? 171
194-What Are the Historical Roots of the Search for Fundamental Particles? 172
195-What Is Antimatter? 172
196-What Is the Relative Abundance of Matter and Antimatter in the
Universe? 173
197-What Is the Particle Zoo? 173
198-How Do Particles Mediate Forces? 176
199-What Are Quarks? 176
200-What Is Color Charge? 178
201-What Are Gluons? 179
202-What Is Quark Confinement? 179
203-What Are Leptons? 179
204-What Is Neutrino Oscillation? 181
205-What Is the Weak Force? 182
206-What Is a Feynman Diagram? 182
207-What Conservation Laws Are Associated with Hadrons and Leptons? 184
208-What Is the Higgs Boson? 185
209-What Is Unification? 185

9 Relativity 187
210-What’s the Difference between Special Relativity and General Relativity? 187
211-How Was Special Relativity Developed? 188
212-What are the Two Principles (or Postulates) of Special Relativity? 189
213-How Are Time and Distance Measurements Affected in Relativity? 190
214-What Are Proper Time and Proper Length? 190
215-How Are Time Dilation and Length Contraction Related? 191
216-What Is the Twin Paradox? 192
217-Can You Travel Backward in Time? 193
218-What Is Spacetime? 193
219-How Are Velocity Measurements Affected by High Speeds? 194
220-What Is the Doppler Effect? 195
221-What Is Relativistic Energy? 196
222-What Are Photons? 198
223-How Is Relativity Connected to Electromagnetism? 199
224-What Is the Principle of Equivalence? 199
225-How Does General Relativity Describe Gravity? 200
226-What Are Some Consequences of General Relativity? 200
227-What Is a Black Hole? 202
228-What Are Gravitational Waves? 203
229-How Do We Use Relativity? 203
230-So Is Everything Really Relative? 204

10 Astrophysics and Cosmology 207
231-What Are Astronomy, Astrophysics, and Cosmology? 207
232-How Was Our Solar System Formed? 208
233-How Was the Moon Formed? 209
234-What Are the Orbits of the Planets? 209
235-What Other Objects Are in the Solar System? 211
236-Why Isn’t Pluto Considered a Planet? 212
237-What Is the Solar Wind? 213
238-What Are Stars? 213
239-How Do Stars Evolve in Time? 214
240-How Are Stars Classified? 214
241-What Is a Supernova? 215
242-What Are Galaxies? 217
243-How Has the Universe Evolved in Time? 218
244-What Is the Evidence for the Big Bang and Expanding Universe? 218
245-How Are Cosmic Distances Determined? 219
246-What Are Dark Matter and Dark Energy? 220
247-Where Do We Go from Here? 221