Optics - lenses, telescopes, microscopes, and optical fibers Each section will open directly in a new window. Close each window as you finish. You might find it helpful to print this list of questions.
1 Rays
Review the rays section in the Optics index.
Essential questions
1 What is the difference between a real and a virtual image?
2 What two rays are the simplest to choose when drawing a ray diagram?
3 What effect does increasing the height of the object in a ray diagram have on the predicted image position?
4 Why is the formula method for predicting the position of an image equivalent to drawing an accurate ray diagram?
5 How many images of a distant light are seen by reflection in a simple two surface lens. What determines where the images are located?
2 The thin lens formula
Review the formula section in the Optics index
Essential questions [Sufficient detail - you do not need all the finer points].
1 By what principle is the lens formula normally proved from ray diagrams?
2 How exactly is the ray diagram drawn for a magnifying glass?
3 How is the formula changed if an image becomes virtual?
4 Is the formula more accurate than a ray diagram (in principle and in practice)?
5 How is the simple convex-lens-real-image-formula modified to predict the image position in a convex mirror?
3 Telescopes
Read the telescope section in the Optics index (Instruments).
Essential questions
1 Which telescope (of historical importance) had a concave eyepiece?
2 How do you find the magnification of a refracting telescope?
3 Who made the first reflecting telescope (and why)?
4 Why are all large modern telescopes reflecting instruments?
4 Microscopes
Read the microscope section in the Optics index (Instruments).
Essential questions
1 Which of the two lenses in a simple microscope has the shorter focal length?
2 Where is the object placed to produce the first (real) magnified image?
3 Where is the final image normally formed?
4 How is the magnification of a microscope related to the power of the component lenses?
5 Optical fibers
Read the optical fiber section in the Optics index (Instruments).
Essential questions
1 What part does total internal reflection play in the operation of a simple glass optical fiber?
2 Why do glass optical fibers have a plastic covering?
3 What wavelength of light is used for the transmission of signals on optical cables (and why)?
4 How is it possible simply to calculate the maximum angle of incidence for which a ray will be totally internally reflected in a simple optical fiber?
6 Lens defects
Read the lens defects section in the Optics index (Instruments).
Essential questions
1 What causes chromatic aberration and how is it countered?
2 What effect on an image is caused by spherical aberration?
3 How might a student reduce spherical aberration in a simple demonstration astronomical telescope?4 How is spherical aberration eliminated in a large astronomical reflecting telescope?
5 What briefly are; barrel distortion, pincushion distortion and coma? When would you be most likely to notice these effects?
7 Two lenses in contact and multiple lenses
Read the two lenses in contact section in the Optics index (Instruments).
Essential questions
1 What is the formula for finding the focal length of two lenses in contact?
2 What is is the definition of the power of a lens?
3 How could you find the focal length of a concave lens using a real image of the Sun?
4 Why is it perfectly sensible (in his own mind) for Dr. Dolittle, in the children's story books, to wear four pairs of glasses at once?
8 Rayleigh's criterion for resolution
Read the Rayleigh's criterion section in the Optics index (Instruments).
Essential questions
1 What is the width of the central maximum of the diffraction pattern of a single slit (I want a formula for it)?
2 How is this relationship modified for a small circular hole?
3 What is Rayleigh's criterion for the resolution of two point sources ..... and why is it somewhat arbitrary?
4 What examples could IB use to ask questions on this topic?
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