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phsyics > 2. Quantum > Flashcards

2. Quantum Flashcards

1
Q

What happens if frequency is below threshold?

A

nothing

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2
Q

What is proportional to intenisty?

A

number of photo electrons emitted per second

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3
Q

What does max kinetic energy increase with?

A

frequency

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4
Q

does intensity affect max kinetic energy?

A

no.

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5
Q

Are photoelectrons emitted with the same Ek or a range?

A

a range

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6
Q

What is emitted from the surface of a metal after light is shone on it?

A

photo electrons

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7
Q

What is shone on the surface of metals?

A

UV radiation

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8
Q

Can threshold frequncy be explained by the wave theory?

A

no

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9
Q

What theory explains threshold frequncy?

A

Einsteins photon model of light

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10
Q

What is threshold frequency?

A

The minimum frequency of photons, required for photoelectrons to be emitted from the surface.

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11
Q

Is the threshold frequency the same for all metals?

A

no

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12
Q

What is meant by the work function of a metal?

A

mimimum energy needed to break bonds and remove electron from a metals surface (as photoelectron)

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13
Q

What is the photoelectric effect?

A

photoelectrons emitted from the surface of a metal after a light above threshold ( certain minimum) frequency is shone on it.

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14
Q

What is an electron volt?

A

work done to accelerate an electron through a pd of 1V

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15
Q

What is a nucleon?

A

a proton or neutron

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16
Q

What is ionisation?

A

the process of:
an atom losing an orbital electron;
becoming larger

16
Q

What letter represents proton number?

A

Z

17
Q

What is excitation ?

A

the process of:
-an electron taking in an exact quantity of energy to:
-move it up to next electron level.

18
Q

What is a photon ?

A

A discrete packet of energy

19
Q

What is stopping potential ?

A

the minimum potential difference, -required for photoelectrons
-to be emitted from a surface

20
Q

What is ground state?

A

The most stable, lowest energy level that an electron can exist in

21
Q

What is the photoelectric effect?

A

the emision of photoelectrons from the surface of a metal after light above a certain frequency is shone on it

22
Q

What is (an initial) high voltage applied to in fluorescent tubes?

A

mercury vapour

23
Q

What do fast moving, free electrons do?

A

ionise some mercury atoms, producing more free electrons

23
Q

What does this high voltage do?

A

accelerates fast moving, free electrons

24
Q

What do newly produced free electrons do?

A

collide with electrons in other mercury atoms, exciting their electrons to higher energy levels

25
Q

What happens when excited electrons return to their ground state?

A

they emit photons in UV range

26
Q

What absorbs UV range photons?

A

phosphor coating inside fluorescent tube

27
Q
A

phsyics (2 decks)

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