3.1.1 - Imaging and signalling (A-Level Physics OCR B H557)

#3.1.1a(i)

the formation of a real image by a thin converging lens, understood as the lens changing the curvature of the incident wave-front

#3.1.1a(ii)

the storage of images in a computer as an array of numbers that may be manipulated to enhance the image (vary brightness and contrast, reduce noise, detect edges and use false colour)

Learners are not expected to carry out numerical manipulations in the examination; an understanding of the nature of the processes will be sufficient

#3.1.1a(iii)

digitising a signal (which may contain noise); advantages and disadvantages of digital signals

#3.1.1a(iv)

evidence of the polarisation of electromagnetic waves.

#3.1.1b

Make appropriate use of:

(i) the terms: pixel, bit, byte, focal length and power, magnification, resolution, sampling, signal, noise, polarisation

by sketching and interpreting:

(ii) diagrams of the passage of light through a converging lens using both wave-fronts and rays

(iii) diagrams of wave-forms.

#3.1.1c(i)

the amount of information in an image = no. of pixels × bits per pixel

#3.1.1c(ii)

power of a converging lens $P = \dfrac{1}{f}$ , as change of curvature of wave-fronts produced by the lens

#3.1.1c(iii)

use of $\dfrac{1}{v} = \dfrac{1}{u} + \dfrac{1}{f}$ (Cartesian convention)

restricted to thin converging lenses and real images

#3.1.1c(iv)

linear magnification

$m = \dfrac{\text{image height}}{\text{object height}} = \dfrac{v}{u}$

#3.1.1c(ix)

the graphical representation of the digitisation of an analogue signal for a given number of levels of resolution

#3.1.1c(v)

$v = fλ$ including the use of $f = \dfrac{1}{T}$

#3.1.1c(vi)

number of bits, b, provides $N = 2^b$ alternatives; $b = \log_2{N}$

#3.1.1c(vii)

minimum rate of sampling > 2 × maximum frequency of signal

#3.1.1c(viii)

rate of transmission of digital information = samples per second × bits per sample

#3.1.1c(x)

use of $b = \log_2{\dfrac{v_{total}}{v_{noise}}}$

#3.1.1d(i)

determination of power or focal length of converging lenses using 3.1.1c(iii)

links to 3.1.1c(ii)(iii), PAG6

#3.1.1d(ii)

observing polarising effects using microwaves and light.

links to 3.1.1a(iv), PAG6

A-Level Physics OCR B H557

3.1.1: Imaging and signalling