3.2.2.2-3 - Collisions Of Electrons And Energy Levels And Photon Emission Flashcards

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1
Q

Where can atoms only exist?

A

In certain energy levels.

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2
Q

How can electrons move down energy levels?

A

By emitting a photon.

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3
Q

Energy gained by electron (eV) =

A

Accelerating voltage (V)

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4
Q

1ev =

A

1.6x10^-19J

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5
Q

What is the energy carried by each photon equal to?

A

The difference in energies between the levels.

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6
Q

hf=

A

E2 - E1

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7
Q

How can electrons move up energy levels?

A

If they absorb a photon with the exact energy difference between the two levels.

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8
Q

What is excitation?

A

An electron is at a higher level than the ground state.

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9
Q

When do we say an atom is ionised?

A

If an electron is removed from an atom.

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10
Q

What is ionisation energy?

A

The amount of energy needed to completely remove an electron from the atom from the ground state.

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11
Q

How do mercury atoms become excited in a fluorescent tube?

A

Electrons flow through the tube and collide with mercury atoms raising the electrons to a higher level.

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12
Q

How are mercury atoms excited to higher energy levels?

A

The flow of free electrons collides with electrons in other mercury atoms.

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13
Q

What happens when these excited electrons return to their ground states?

A

They emit photons in the UV range.

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14
Q

What is the purpose of the coating on the inside surface of the glass in a fluorescent tube?

A

Photons emitted from mercury atoms are in the ultraviolet spectrum. These photons are absorbed by the powder coating and the powder coating emits photons in the visible spectrum.

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15
Q

How is visible light produced?

A

The electrons cascade down the energy levels, emitting many lower energy photons in the form of visible light.

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16
Q

What is a line spectrum seen as?

A

A series of bright lines against a black background.

17
Q

In the line spectrum what does each line correspond to?

A

A particular wavelength of light emitted by the source.

18
Q

What do hot things emit?

A

A continuous spectrum in the visible and infrared.

19
Q

Why are all wavelengths allowed in the continuous spectra?

A

The electrons are not confined to energy levels in the object product the continuous spectrum.

20
Q

What do you get when light with a continuous spectrum of energy passes through a cool gas?

A

A line absorption spectrum.

21
Q

Where will electrons be at low temperatures?

A

In their ground states.

22
Q

What do the photons have to be in order to be absorbed by the electrons?

A

The photons have to have energies equal to the difference between two energy levels.