Energy Levels And Photo Emission

Question 0

Each level is given a number. What number represents the ground state

Answer 0

N=1

Question 1

What do electrons in an atom exist in

Answer 1

Discrete/well-defined energy levels

Question 2

Electrons can move …. An energy level by emitting a ….

Answer 2

Down

Photon

Question 3

Why can the energy of each photon emitted only take a certain allowed value

Answer 3

Since the TRANSITIONS are between DEFINITE ENERGY LEVELS

Question 4

What do we use instead of the unit joules and why

Answer 4

ELECTRONVOLT (eV)

The ENERGIES involved are so TINY

Question 5

What is the definition of an ELECTRONVOLT (eV)

Answer 5

The KINETIC ENERGY carried by an electron

After it has been ACCELERATED through a PD of 1 volt

Question 6

What does the energy gained by an electron (eV) equal

Answer 6

That accelerating voltage (V)

Question 7

What does 1 eV equal in joules

Answer 7

1.6*10-19

Question 8

What is the energy carried by each photon equal to

Answer 8

The difference in energies between two levels

Question 9

Should you be concerned that the energy is negative

Answer 9

No. Don’t worry about it

Question 10

Write down the equation for a transition between two energy levels

Answer 10

E=e1-e2=hf=hc/y

Question 11

What do fluorescent tubes use to produce light

Answer 11

Excited electrons

Question 12

What does fluorescent tubes contain

Answer 12

MERCURY VAPOUR

Across which a HIGH VOLTAGE is applied

Question 13

What happens caused by the high voltage being applied to the mercury vapour

Answer 13

The ELECTRONS in the MERCURY
COLLIDE
With the FAST-MOVING FREE ELECTRONS (accelerated by the HIGH VOLTAGE)
They’re EXCITED to a higher ENERGY LEVEL

Question 14

After the electrons are excited to a higher energy level, what happens to them

Answer 14

When they return to their GROUND STATE

They emit PHOTONS in the UV range

Question 15

What costing is on the inside of the fluorescent tube

Answer 15

Phosphorus

Question 16

What does the phosphorus coating on the inside of the tube do

Answer 16

ABSORB the PHOTONS
EXCITING it’s ELECTRONS to much higher ORBITS

ELECTRONS then CASADE down the ENERGY LEVELS
EMITTING many LOWER ENERGY PHOTONS
In the form of VISIBLE LIGHT

Question 17

Fluorescent tubes product what (in terms of spectra)

Answer 17

Line emission spectra

Question 18

What are the two ways you could split tight from a fluorescent tube

Answer 18

Prism

Diffraction grating

Question 19

If you split the light from a fluorescent tube with a prison or a diffraction grating what do you get

Answer 19

Line spectrum

Question 20

What is a line spectrum seen as

Answer 20

SERIES of
BRIGHT LINES against a
BLACK BACKGROUND

Question 21

What does each LINE correspond with

Answer 21

A PARTICULAR WAVELENGTH of light EMITTED by the source

Question 22

Why are their only certain corresponding wavelengths

Answer 22

Since only CERTAIN PHOTON ENERGIES are ALLOWED

Question 23

What does shining white might through a cool gas give (in terms of spectrum)

Answer 23

ABSORPTION SPECTRUM

Question 24

What does the continuous spectra contain

Answer 24

All POSSIBLE wavelengths

Question 25

State a spectrum which is continuous

Answer 25

White light

Question 26

What happens if you split white light up with a PRISM

Answer 26

COLOURS all MERGE into each other

There are NO GAPS

Question 27

Other that white light, what also emits a continuous spectrum and in what

Answer 27

HOT THINGS in the VISIBLE and INFRARED

Question 28

What does cool gases do to a continuous spectrum

Answer 28

REMOVE CERTAIN WAVELENGTHS

Question 29

You get a ….. ….. ….. When light with a ….. ….. Of …. (…. ….) passes through cool gas

Answer 29

LINE ABSORPTION SPECTRUM
CONTINUOUS SPECTRUM
ENERGY
WHITE LIGHT

Question 30

Explain why we get a line absorption spectrum when we shine white light through a cool gas

Answer 30

At low temp, most ELECTRONS in the gas atoms will be in their GROUND STATE
PHOTONS of the CORRECT wavelength are ABSORBED by the electrons to excite them to higher energy levels

Question 31

What then happens to the photons of the correct wavelength absorbed by the electrons in the gas atoms

Answer 31

MISSING from the CONTINUOUS SPECTRUM when it comes out the other side of the gas

Question 32

What do the black lines in the continuous spectrum correspond to

Answer 32

the ABSORBED WAVELENGTH

Question 33

What would you expect if you compared the absorption and emission spectra of a particular gas

Answer 33

The black lines in the absorption spectrum match up with the bright lines in the emission spectrum