Is my answer correct?

[FlorianK]

Standard Figure of Youngs-Double-Slit experiment is shown.

Use appropriate physics principles to explain the existence of the dark bands within the pattern.

Dark bands occur when destructive interference occurs.
Destructive interference ovvurs when the light waves from Slit 1 and 2 are exactly (1/2+n , n E Z) wavelength out of phase. This means that they cancel each other out and create an anti-nodal point.


Explain how the existence of discrete energy levels is evidence for the wavelike nature of electrons in the atom.

Electrons must be considerd wavelike properties as they can only exist in discrete energy levels around the nucleus.
These energy levels correspond to standing waves where only certain wavelength are feasible for a stable level.

A figure is shown with 2 transformers and the 2 solenoids are conected with a soft iron core.
Explain the prupose of the soft iron core in this experiment
The purpose of the soft iron core in this experiment is to increase the 'flux-linkage' considerable by concentrating and hence strengthening the magnetic field created.

A spectroscope is used to observe the light emitted from the gas when the electrons are fired through it, and a number of coloured bands are observed which correspond to specific wavelength being emitted. The spectroscope is also used to view the effect of shining white light through the gas and a number of dark bands are observed. It was however, that there are fewer dark bands than there are bright bands. Explain why fewer dark bands would be expected.

For an atom to absorb light (dark band) the energy of the incoming photon must be equal to the exact difference between the ground state energy level and the energy level of one of the sub-shells. For an atom to emit light (bright band) the energy of the emitted photon can be any of the diffrence between subshells or between the ground-state and a subshell. Hence, there are more possibilities to emit light than absorb.

Thx, help is highly appreciated.

[billyjackson768]

Standard Figure of Youngs-Double-Slit experiment is shown.

Use appropriate physics principles to explain the existence of the dark bands within the pattern.

Dark bands occur when destructive interference occurs.
Destructive interference ovvurs when the light waves from Slit 1 and 2 are exactly (1/2+n , n E Z) wavelength out of phase. This means that they cancel each other out and create an anti-nodal point.

This sounds great, right up until the last bit. The dark bands from destructive interference are nodes, not anti nodes.

Explain how the existence of discrete energy levels is evidence for the wavelike nature of electrons in the atom.

Electrons must be considerd wavelike properties as they can only exist in discrete energy levels around the nucleus.
These energy levels correspond to standing waves where only certain wavelength are feasible for a stable level.

Sounds to be on the right track to me. I'm not sure if you would need to go into any more detail through. For 3 marks to be safe I would probably explain a little bit more about those standing waves and why they must only exist at levels where an exact number of wavelengths can fit.

For the second last one I'm not to sure exactly what the setup looks like, you're probably on the right track though.

Then for the last one... I'm not so sure. It sounds, pretty good though. 

[FlorianK]

Thx

I'm not quite sure of the concept so I might be wrong.

Electrons of 5.0eV are fired through a gas Q and emerge with energies of 1.2eV, 1.8eV, 3.0eV and 5.0eV
If the ground state is 0eV, what is the energy of the second excitation state?
What I thought was:
Ground level 5.0-5.0=0
First Exited: 5.0-3.0=2
Second Exited: 5.0-1.8=3.2
Third Exited: 5.0-1.2=3.8

The solution says the answer would be 3.8eV ~_~?!?