Quiz

Below is a concise set of flashcards (Question on one side, brief Answer on the back). Each card is short enough to fit neatly on a single card. Happy studying!

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### Flashcard 1

Q: How do astronomers measure cosmic elemental abundances, and why does it matter?

A: They measure emission/absorption lines in light from cosmic objects. Each element’s “fingerprint” reveals how much is present. It’s crucial for testing Big Bang models and understanding how the universe evolves chemically.

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### Flashcard 2

Q: What are the cosmic abundances of hydrogen, helium, and everything else?

A: About 90% hydrogen, 9% helium, and ~1% all other elements.

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### Flashcard 3

Q: How do temperature and energy density change as the universe expands?

A: Both drop with expansion (lower density, lower temperature). If compressed, both increase.

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### Flashcard 4

Q: What happens if you heat an atom or a nucleus enough?

A: First the electrons get stripped off (ionization). At even higher temperatures (~10^9 K), the nucleus itself breaks into protons and neutrons.

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### Flashcard 5

Q: Which eras did particle, nuclear, and atomic physics dominate, and when?

A:

- Particle Physics: <1 second after the Big Bang

- Nuclear Physics: ~1 second to 300,000 years

- Atomic Physics: ~300,000 years onward

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### Flashcard 6

Q: What are alpha, beta, and gamma radiation, and which is the most dangerous?

A:

- Alpha: Helium nuclei (least penetrating)

- Beta: High-energy electrons (medium)

- Gamma: High-energy photons (most penetrating and typically most dangerous externally)

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### Flashcard 7

Q: What is the basic model of the atom, and how big is the nucleus compared to the whole atom?

A: A tiny nucleus of protons/neutrons in the center, electrons around it. The nucleus is thousands of times smaller—like a blade of grass in a stadium.

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### Flashcard 8

Q: How do a cloud chamber and a Geiger counter detect radiation?

A:

- Cloud Chamber: Vapor condenses along charged particle tracks

- Geiger Counter: Ionized gas causes an electrical pulse

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### Flashcard 9

Q: What is the electric force law?

A:

\[

F = k\,\frac{q_1 q_2}{r^2}

\]

It’s an inverse-square force that can attract or repel, depending on the charges’ signs.

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### Flashcard 10

Q: What is an isotope, and how can you find protons, neutrons, and electrons from its symbol?

A: Isotopes have the same number of protons (same atomic number) but different neutrons. In \(\,^{A}_{Z}\text{X}\):

- \(Z\) = protons = electrons

- \(A\) = protons + neutrons

- Neutrons = \(A - Z\).

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### Flashcard 11

Q: What is a half-life, and how does radioactive dating work?

A: Half-life: time for half a radioactive sample to decay. In dating (e.g., carbon dating), measuring remaining radioactive isotopes tells you how long ago the material stopped exchanging isotopes with the environment.

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### Flashcard 12

Q: What are the ages of the Earth and the universe?

A: Earth is about 4.5 billion years old; the universe is about 13.8 billion years old.

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### Flashcard 13

Q: What holds the nucleus together, and what is binding energy?

A: The strong nuclear force overcomes proton repulsion. Binding energy is the mass difference (via \(E = mc^2\)) that’s released when nucleons fuse into a nucleus.

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### Flashcard 14

Q: Compare nuclear fission vs. fusion, and explain chain reactions.

A:

- Fission: Splitting heavy nuclei (e.g., uranium) to smaller ones. Can cause a chain reaction if released neutrons trigger more fissions.

- Fusion: Fusing light nuclei (e.g., hydrogen) into heavier. Both processes release energy; fusion typically needs higher temperatures.

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### Flashcard 15

Q: What are peaceful and non-peaceful applications of fission and fusion?

A:

- Fission: Nuclear power reactors (peaceful), atomic bombs (non-peaceful).

- Fusion: Research reactors for clean energy (peaceful), hydrogen bombs (non-peaceful).

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### Flashcard 16

Q: How does the universe’s expansion produce hydrogen and helium?

A: After the Big Bang, as the universe cooled, protons and neutrons fused briefly to form helium (and hydrogen stayed as single protons). This primordial nucleosynthesis set the ~90% H / ~9% He ratio.

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Use these flashcards for active recall: read the question side, try to answer, then check the answer side. Good luck!