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Physics > Matter And Radiation > Flashcards

Matter And Radiation Flashcards

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0
Q

How are electrons held in the atom?

A

Their negative charge attracts the positively charged nucleus through the electrostatic force

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1
Q

What is a nucleon?

A

A proton or neutron in the nucleus

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2
Q

What is an isotope?

A

Atoms of the same element with different numbers of neutrons

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3
Q

Why must the protons remain the same in an isotope?

A

Otherwise it would be an atom of a different element

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4
Q

What is the nucleaon number?

A

The total number of protons and neutrons in the atom

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5
Q

What is specific charge?

A

Charge dived by mass

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6
Q

What does the strong nuclear force do?

A

Overcomes the electrostatic force of repulsion between protons and keeps the protons and neutrons together

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7
Q

When does the strong force not hold the neutrons and protons together?

A

In an unstable nuclei

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8
Q

What is the range of the strong nuclear force?

A

3-4 femtometers

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9
Q

True or false - the strong nuclear force only works on two protons?

A

False - It has the same effect on two protons, two neutrons or a proton and a neutron

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10
Q

At what distance will it attract?

A

Between 0.5 fm and 3-4fm - any distance before 0.5fm it will repel

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11
Q

What is alpha decay?

A

When an alpha particle ( 2 protons and 2 neutrons) is emitted from a nucleus

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12
Q

What is beta decay?

A

When a neutron in the nucleus changes into a proton. A beta ( electron) is emitted along with an anti neutrino

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13
Q

What is gamma radiation?

A

It is electromagnetic radiation with no mass or charge. It occurs when an atom has too much energy, following an alpha or beta emission.

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14
Q

How were neutrinos and anti neutrinos detected?

A

When scientists measured the energy of beta particles emitted, the results varied up to a maximum. Some of the energy was being carried away by mysterious particles - neutrinos and antineutrinos

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15
Q

What is light often expressed in?

A

Nanometers ( 1x10-9)

16
Q

what is the wavelength of visible light ?

A

400nm - 700nm

17
Q

what does an electromagnetic wave consist of?

A

an electric wave and magnetic wave that travel at 90 degrees to each other and the direction of energy. They are also in phase

18
Q

what is a photon ?

A

when electromagnetic waves are emitted, they are emitted in bursts, each burst is a packet of energy - a photon

19
Q

what does a laser beam consist of?

A

photons of the same frequency

20
Q

what is the power of a laser beam?

A

Energy per second transferred by the photons

21
Q

What happens when matter and antimatter meet?

A

They destroy each other releasing radiation - Annihilation

22
Q

What radiation is released when a positron and electron meet?

A

Gamma photons

23
Q

How does a PET scanner work?

A

A positron emitting isotope is administered and som of it reaches the brain. A positron reaches an electron, emits photons and a computer creates an image

24
Q

How are positron emitting isotopes manufactured?

A

A stable isotope is placed in a path of a beam of protons. Some of the nuclei gain protons and become unstable.

25
Q

What are the similarities and differences of particles and antiparticles?

A

They have the same rest mass but exactly the opposite charge

26
Q

What is pair production?

A

When a photon with sufficient energy changes into a particle-antiparticle pair which then separates from each other

27
Q

What is 1 electron volt?

A

The energy transferred when an electron is moved through a potential difference of 1 volt

28
Q

How was the positron discovered?

A

In a cloud chamber with a magnetic field, beta decay shows an electron bending towards positive. Carl Anderson noticed a particle bend towards the negative - a positron

29
Q

What happens when two objects interact?

A

They exert equal and opposite forces on each other

30
Q

What does the weak nuclear force do?

A

Neutrons to change into photons in beta- decay and vice versa for beta+

31
Q

What particle is exchanged by the weak nuclear force?

A

W boson

32
Q

What are the differences between w bosons and photons?

A

They have a non-zero rest mass, very short range of around 0.001fm and are positively or negatively charged

Physics (7 decks)

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