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20 Cards in this Set
- Front
- Back
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What does the permittivity of free space E0 relate to? |
Electric field strength due to a charged object in free space |
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What does permeability of free space u0 relate to? |
Magnetic flux density due to a current-carrying wire in free space |
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Inertial frame of reference |
Frame of reference that has a constant velocity |
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At stopping potential, what is Ek(max) equal to? |
eVs |
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TEM: first lens |
Magnetic condenser lens Forces elections into a parallel beam directed at a very thin sample sample |
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TEM: second lens |
Objective lens Deflects the scattered electrons so they form an enlarged, inverted 'first' image |
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TEM: third lens |
Magnifier lens Focuses the electrons from the central area of the first image to form a magnified final image on the screen |
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Resolving power |
The least separation between 2 objects in an image produced by a microscope that can just be seen apart |
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TEM: do you want a large or small Dr Broglie wavelength? |
Small - less diffraction so greater resolving power |
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2 factors which cause limitations on the detail in a TEM image |
Sample thickness - electrons suffer a slight loss of speed passing through the sample Lens aberrations: the magnetic field from the outer and inner parts of the lens gap may focus electrons from a given point to different positions on the screen, causing blurring |
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STM: the gap is sufficiently small so |
The amplitude is finite on the other side Small changes in the gap produce measurable changes in the number of electrons per second crossing the gap |
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3 things about the photoelectric effect that couldn't be explained using wave theory |
The existence of a threshold frequency That although number of electrons emitted per second is proportional to frequency of incident radiation, no electrons at all are emitted if the frequency is lower than the threshold frequency Photoelectric emission occurs without delay as soon as the incident radiation is directed at the surface |
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What is a black body and why is it used for the curves |
Perfect absorber of EM radiation Used as it emits a continuous spectrum of wavelengths |
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When does a dipole detector give 0 signal? |
When the dipole is perpendicular to the plane of polarisation of the oscillating electric field |
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What did wave theory predict about the black body radiation curves? |
As wavelength gets smaller, intensity of the black body radiation from a hot object should approach infinity |
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Why should a voltmeter have a high resistance? |
So charge isn't lost through it |
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Bertozzi graph |
Kinetic energy against v/c |
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How to work out uncertainty from results |
Half the range |
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Why did Planck's hypothesis solve the ultraviolet catastrophe? |
Radiation is emitted in quanta The quantum is related to a single frequency An energy quantum is hf So high-frequency radiation is emitted in larger chunks of energy |
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Newton's explanation of refraction |
Corpuscles attracted into the substance Components of velocity perpendicular to the boundary of each corpuscle is increased - the component of velocity parallel to the boundary is unchanged |
