Cambridge A2 Physics (9702) Flashcards By Al-Hassan (V3)
Physics
This contains flashcards for the CIE A2 Physics syllabus from Chapter 12: Motion in a Circle to Chapter 25: Astronomy & Cosmology.
Sample Data
| Front | Explain how the contrast and sharpness, thus the resolution, of a medical image generated by X-ray medical imaging is improved. |
| Back | - we define contrast as:> the difference in the degree of blackening between structures- contrast allows a clear difference between tissues to be observed- X-ray image contrast can be improved (increased) by:> using the correct level of X-ray hardness:>> X-ray hardness is a measure of the penetrating power of X-rays>> use hard X-rays for bones and soft X-rays for tissue:>>> hard X-rays have a higher frequency and shorter wavelength, soft X-rays have a lower frequency and a longer wavelength> using a good contrast media, which is an absorber of X-rays, such as barium or iodine:>> the imaged patient swallows this contrast media- we define sharpness as:> how-well defined the edges of structures are- X-ray image sharpness can be improved (increased) by:> using a narrower X-ray beam> reducing X-ray scattering by using a collimator or lead grid> smaller pixel size |
| Front | Describe the features of a radial electric field. |
| Back | - the field lines are equally spaced as they leave the surface of the +ve test charge, but the distance (separation) between the field lines increases with increasing distance from the +ve test charge causing the electric field- the electric field strength decreases with distance from the +ve test charge producing the electric field- the magnitude of the force acting on a +ve test charge decreases with increasing distance from the +ve test charge producing the field |
| Front | Explain how to determine the electric potential difference from a electric field strength-distance graph. |
| Back | - the electric potential difference due to a charge present in an electric field can be calculated using the area under an E-r graph- a graph of E against r can be drawn for a +ve or -ve point charge of Q- this is a graphical representation of the equation used to a calculate the radial electric field strength due to a point charge:> E = Q/4πε0r2 - the area under the E-r graph between two points is equal to the electric potential difference, ∆Ve, between those two points
 - the key features of the E-r graph above are:> all values of E are -ve for a -ve point charge, -Q> all values of E are +ve for a +ve point charge, +Q> as r increases, E decreases as E against r follows the E ∝ 1/r2 (inverse square law)> the area under the graph above is the change in electric potential, ∆Ve > due to the inverse square law relationship between E and r, this graph is steeper than the corresponding V-r graph covered in the previous flashcard
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