Waves (1) - reflection, refraction, prisms and apparent depth 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 Huygens' principle
Read the Huygens' principle section in the Waves index.
Essential questions
1 What is meant by an envelope of wavelets?
2 Are Huygens' wavelets real, or are they merely geometrical constructions?
3 What wave phenomena can be "predicted" by using Huygens' principle?
2 Snell's law
Read the refraction section in the Ripple tank index and the Snell's law section in the Optics index.
Essential questions
1 What exactly is Snell's law, and how are the angles of incidence and refraction defined.
Note the order of increasing refractive index for ... air, water, glass, diamond.
2 How does one find an angle of refraction when given an angle of incidence and the refractive index?
3 How is refractive index related to the wavelength and velocity of light in glass?
4 How is Snell's law applied to the interface between ... say ... water and glass?
3 Lenses
Read the rays section in the Optics index.
Read the lenses section in the optics index. Convex lenses (real image) (virtual image) and concave lenses.
Essential questions
1 What is meant by real and virtual and what alternative description could be applied?
2 What do the symbols u, v and f represent?
3 How could a student find the possible error in v (image distance) when using a screen to find images formed by a convex lens?
4 How is the focal length of a convex lens determined most easily?
5 What is the method of no parallax and what is it used for?
Multiple lenses in contact
Read the two lenses in contact section in the Instruments index.
Essential questions
1 What is meant by the power of a lens?
2 How is the focal length of a concave lens determined most easily?
4 Mirrors and lenses
Read the plane mirror section in the Mirrors index.
Essential questions
1 Where is the image in a plane mirror and how is it found with a ray diagram?
2 What is the effect that makes a right-hand glove appear as a left-hand glove in a plane mirror?
3 How is light returned from a right-angled corner?
4 How many images appear when an object is placed in a two dimensional right-angled corner?
5 How many images appear when an object is placed in a three dimensional right-angled corner?
Read the sections on convex and concave mirrors in the Optics index.
Essential questions
6 What is the difference between the focal points of a circular (spherical) and a parabolic mirror?
7 How is the focal length of a thin circular mirror related to the radius of curvature?
8 Under what conditions is a real image formed in a concave mirror?
9 Describe the image formed in a convex optical mirror?
10 How large must a parabolic mirror be to effectively Essential the sounds of bird song?
5 The thin lens formula
Read the thin lens formula section in the Optics index
Essential questions
1 On what mathematical principle does the derivation of the lens formula depend?
2 What is meant by a 'thin' lens?
3 What assumptions are made when the ray diagram is drawn which lead to an approximate formula in a real case?
4 What happens to the value of the image distance v as the radius of curvature of a concave mirror approaches infinity?
6 Total internal reflection
Read the reflection section in the Optics index and the Helium-neon laser section in the Instruments index.
Essential questions
1 Why is this type of reflection referred to as total?
2 Why is this type of reflection referred to as internal?
3 How exactly is the critical angle for total internal reflection related to the refractive index of the two materials?
4 What is an interference film mirror?
5 What is the Brewster angle?
7 Prisms and Apparent depth
Read the prisms section in the Optics index.
Essential questions
1* Newton is often credited with the first description of spectral colors. How appropriate is this assessment?
2 How does the dispersion of light by a prism compare with the dispersion by a diffraction grating?
3 What is meant by minimum deviation and when does it occur?
4 How is a prism used to measure refractive index?
5 How is apparent depth used to measure refractive index?
8* Refraction in the atmosphere
For interest and background - IB is unlikely to ask specific questions on these topics, but they did one year ask a general question on the rainbow. Very few candidates provided even rudimentray answers.
Read the essays: Ice Crystal Halos, Mirage simulations, and Green-flash simulations in the Essays index.
Read Rainbows in the Essays index.
Essential questions
1 What critical role does minimum deviation play in the formation of ice crystal halos and of rainbows?
2 What is the difference between superior and inferior mirages, and what temperature gradients lead to their formation?
3 Why is the green flash green and not blue?
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