Extended writing questions - lenses, refraction etc...

Some ideas for possible questions...

1) Describe an experiment you could do, including the measurements you would need to take, to determine the refractive index of a transparent block.

2) Compare the similarities and differences between images formed by a magnifying glass and a diverging lens.

3) Describe the factors which affect the focal length of a lens and explain how the lenses in modern glasses can be manufactured to be very thin.

4) Describe an experiment that could be carried out to determine the critical angle of a glass block.

5) Explain how total internal reflection occurs. Why is total internal not possible if light is travelling in air towards a glass surface?

6) Explain how an endoscope works and it's uses in medicine.

Answers to follow shortly.

Test yourself markscheme - Refraction, refractive index and total internal reflection

Mark scheme for exam questions - How did you do???

(a)   (i)    Critical angle

       (ii)   The light is totally internally reflected. 

       It would be insufficient to simply say that ‘the light is reflected’ or even 

      ‘reflected back into the block’.

       (iii)   refractive index =  1/ sin c 

                                        = 1/ sin 42

                                        = 1/ 0.669 = 1.5

       Alternatively the equation refractive index = sin i/sin r could have been used.      

       However, if you use this equation you must imagine the light to be travelling from

       air into glass and not the other way around. So take the angle of incidence as 

       either 31° or 49° with the associated angle of refraction either 20° or 30°.

(b)

• An endoscope has two bundles of optical fibres. 
• Light that is directed into one bundle travels from one end to the other by being totally internally reflected many times. 
• The light is then reflected back through the second bundle of optical fibres.
• The image is viewed through a lens, 
• or if a miniature camera is attached to the optical fibres the image can be displayed on a computer screen.

    It is perfectly okay to answer a ‘prose’ type question using bullet points. However, if 

    you do, make sure each bullet point is a complete sentence.

Extended Writing Questions X-rays and Ultrasounds

Nearly there... 

Some possible ideas for long answer questions for this topic

1) What is ultrasound? Describe some uses of ultrasound in medicine.

2) What are X-rays? Describe how they are created, some of their medical uses and why radiographers have to take care when using them.

3) Compare and contrast the uses of X-rays, CT scans and ultrasonographs in medicine.  Explain the suitability of each kind of scan for its intended purpose.