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AS Unit G491 - Physics in Action

Chapter 1 - Imaging

Title Description
Task 1 - Can I do the maths? These simple exercises are designed to show you the importance of learning to use your calculator properly (you may find the results of your calculations surprising!) and give you an idea of the slightly higher level of mathematical fluency required at AS level, through practising the rearrangement of algebraic formulae.
Task 2 - Forming images with visible light. Your teacher will show you a few useful images to demonstrate how light forms images.  Simple images formed in a pinhole camera are considered first, and then images formed by a convex lens.

Note: this website shows how you can make a simple pinhole camera from a digital SLR, and this website shows how to make a simple pinhole camera which projects onto tracing paper.
Task 3 - Measuring lens power - practical task 1. Estimate the focal length of 2 lenses using the simple method your teacher shows you (note: this method is only an approximation)

2. Carry out lens practical according to your teachers instructions:

• Vary the distance between the object (lamp filament) and the lens.  Measure the corresponding distances from the lens to the focused image.  You must collect at least 6 values!

• Plot a graph of the curvature of the emerging waves (1/v) on the y-axis against curvature of the incident waves (1/u) on the x-axis.

• Find the intercept with the x-axis or the y-axis (whichever is easiest!) - this is the lens power in Dioptres.

• Calculate the focal length of the lens as the reciprocal of the lens power.

Use this method to find the focal length / power of at least 2 lenses.
Task 4 - Two ways of looking at light Light can be though of as either rays travelling in straight lines away from a source, or as wavefronts spreading out in all directions.  Read this document, which has some simple diagrams and explanations to show you the two ways of thinking about light, and how this affects our understanding of a lens.
Task 5 - Investigating the principles of a converging lens (ICT) Look at this computer simulation to illustrate the principles of a simple converging lens.  Investigate the scenarios on this sheet and record your results in your exercise book.
Task 6 - Lens calculations (theory) You need to be able to use the lens equation to solve problems involving the formation of real images by a thin converging lens.  Stick this sheet with the lens equation and this sheet of problems (powerpoint version for teacher here) into your book.  Your teacher will show you how to do the first problem as an example. 
Task 7 - More lenses problems Worksheet - "Q150S - lenses cameras and eyes"
Task 8 - Magnification Your teacher will explain how magnification is defined and how it is calculated.  You will want a copy of this diagram to stick in your exercise book.
Task 9 - Magnification problems This pdf document of mixed exam questions has several questions on magnification.  Try question 6 on page 1 and question 7 on page 5.
Task 10 - Capturing images with CCD's Digital cameras use a device called a CCD to capture images.  You need a basic understanding of how a CCD works.  Your teacher will explain this to you (powerpoint slide of CCD here).  Stick in this diagram of a CCD and write a simple explanation in your exercise book.
Task 11 - Information theory and the binary counting system Getting Used to the Binary Counting System - worksheet

Look at these questions which will give you practice converting between bits, bytes, kilobytes and megabytes.
Task 11b Try these questions, which look at the amount of data required to store an image.

Year 12 "images as pixels" starter questions for subsequent lesson. 

Bits and bytes in images - worksheet (scale down to A5)

How much information in an image - worksheet (also including data rates for information transmission).
Task 12a - Resolution Look at these images of a famous politician.  What do you notice about the quality of the images?  What effect does the number of pixels have on the features that can be identified?

Your teacher will explain to you what is meant by the resolution of an image, and how you can calculate the resolution of one of these images.
Task 12b - Resolution Load each of the files in Scion Image:

1.Identify a feature you recognise, estimate its dimensions.

2. Zoom in until you can see individual pixels

3. Count the pixels comprising the feature and calculate the 'size' represented by one pixel using the dimensions you estimated.

File 1 - x-ray of a hand

File 2 - optical image of a star (assume radius to be ~1×106 km)

File 3 - flower (scale given)

File 4 - space shuttle (wingspan ~24m)

Fill in your answers on this worksheet.
  Now: suggested exam question to try - G491 June 2009 Q8

G491 Jan 2009 Q2
Task 13 - Imaging in X-rays We are not limited to 'looking' at objects using just visible light.  This task requires you to interpret information from an x-ray image of the Kepler Supernova Remnant.
Task 14a - Image Processing using Scion Image Try enhancing each of the images below using filters (filters can be found in the "Process" menu).

File 1 - Mercury with noise (try removing the noise - rank filter)

File 2 - Space shuttle (try the edge sharpening filter & this Laplace kernel)

File 3 - Volcanoes on Io

File 4 - Pele Volcano in UV

How could we darken the whole image?  or lighten it?  Try using the "add" filter from the "arithmetic filters" menu.  Try adjusting the value of the parameter from the default.  What is this doing to the pixel values?

Now try using the "multiply" filter.  What does this do to the pixel values?  What would be the difference between darkening the image using the "add" filter and using the "multiply" filter?
Task 14b - Image Processing Storing images electronically allows us to apply a wide range of analysis / enhancement techniques.  This worksheet will help develop your understanding of how image processing algorithms work , by directly manipulating some sample pixel values.  You will also need these spare grids to record your results.
Task 14c - Image processing Suggested exam questions:

Jan 2010 Q2 (section A, 2 marks)
Task 15 - What is an image Starter task - powerpoint presentation.
Task 16a - Waves for Imaging We can image using a wide range of different waves - look at this presentation to see some examples.

You will be using the wave equation throughout your studies.  You met the wave equation in year 10, so you'll be familiar with it already but you are going to need more practice using it.  Try these questions for homework.

Q10S - speed wavelength and frequency
Task 16b - Ultrasound imaging Your teacher will show you this powerpoint presentation and explain how ultrasound images are obtained.  When you are happy you understand stick in these diagrams (diagram 1 and diagram 2) and write an explanation.  Include these terms in your explanation.
Task 16c - Ultrasound measurements of a pendulum Your teacher will show you an "ultrasonic tape measure" and explain how it works. Now answer these questions about a simple ultrasonic position measuring system, used to track the position of a pendulum against time.
Task 16d - imaging with a Scanning Tunnelling Microscope (STM) Look at this image, taken with an scanning electron microscope (known as an STM or SEM).  What is the image of?  Your teacher will explain how an STM works.  When you are happy you understand stick in this diagram, which shows how the STM works, and answer the questions on this sheet.  You will also need a high resolution copy of the image.
Task 17 - Holiday Homework Task

Due Thursday 8th November 2012

 Complete these mixed exam questions (Microsoft Word document).  Print the questions and answer them on the sheet, or answer the questions on lined paper, or drop into MS14 to pick up a paper copy.
   
Imaging summary questions Answer these questions to check you have understood everything you have learned so far.
Key wave terms - a quick reminder Your teacher will help remind you of some key wave terms and definitions, by creating waves on a rope and a slinky to help jog your memory!

Now, quickly make a note of the keywords and definitions you need to accurately describe and explain wave phenomena.  You should also note down the 3 key formulae you will be using.
Polarisation Your teacher will give you a polarising filter each.  Investigate how a polarising filter affects the glare from several partially reflecting surfaces.

Your teacher will demonstrate horizontally and vertically polarised waves on a rope, and show you the how a simple cardboard polarising filter can affect the waves passing through.

Look at these images of polarised waves passing through filters (powerpoint format).  Your teacher will give you copy of both images (image 1 and image 2) to stick in your book and show you this applet to help explain how polarising filters work.

Now: suggested exam question to try - June 2006 Q2