Light (continued)
Übersicht
A straw looks bent in a glass of water, a diamond sparkles with rainbow fire, and a tiny camera lens captures a whole landscape. All of these come from one idea: light changes speed and bends when it crosses between materials. Control that bending and you can focus, magnify, trap light in a fibre, or split white light into its colours.
In this lesson you will master refraction and refractive index, the critical angle and total internal reflection (with its use in optical fibres), the action of converging and diverging lenses, ray diagrams for real and virtual images, the dispersion of white light by a prism, and the seven colours of the spectrum. Every calculation is shown with its equation, substitution and units.
Ziele
- Define and use the terms normal, angle of incidence and angle of refraction
- Describe an experiment to show refraction of light by transparent blocks of different shapes
- Describe the passage of light through a transparent material (limited to the boundaries between two mediums only)
- State the meaning of critical angle
- Describe internal reflection and total internal reflection using both experimental and everyday examples
- Describe the action of thin converging and thin diverging lenses on a parallel beam of light
- Define and use the terms focal length, principal axis and principal focus (focal point)
- Draw and use ray diagrams for the formation of a real image by a converging lens
- Describe the characteristics of an image using the terms enlarged/same size/diminished, upright/inverted and real/virtual
- Know that a virtual image is formed when diverging rays are extrapolated backwards and does not form a visible projection on a screen
- Describe the dispersion of light as illustrated by the refraction of white light by a glass prism
- Know the traditional seven colours of the visible spectrum in order of frequency and in order of wavelength
- [Supplement] Define refractive index, n, as the ratio of the speeds of a wave in two different regions
- [Supplement] Recall and use the equation sin i n = sin r
- [Supplement] Recall and use the equation n = 1 / sin c
- [Supplement] Describe the use of optical fibres, particularly in telecommunications
- [Supplement] Draw and use ray diagrams for the formation of a virtual image by a converging lens
- [Supplement] Describe the use of a single lens as a magnifying glass
- [Supplement] Describe the use of converging and diverging lenses to correct long-sightedness and short- sightedness
- [Supplement] Recall that visible light of a single frequency is described as monochromatic
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Unterrichtsbewertung
Herzlichen Glückwunsch zum Abschluss der Lektion über Light (continued). Jetzt, da Sie die wichtigsten Konzepte und Ideen erkundet haben,
Sie werden auf eine Mischung verschiedener Fragetypen stoßen, darunter Multiple-Choice-Fragen, Kurzantwortfragen und Aufsatzfragen. Jede Frage ist sorgfältig ausgearbeitet, um verschiedene Aspekte Ihres Wissens und Ihrer kritischen Denkfähigkeiten zu bewerten.
Nutzen Sie diesen Bewertungsteil als Gelegenheit, Ihr Verständnis des Themas zu festigen und Bereiche zu identifizieren, in denen Sie möglicherweise zusätzlichen Lernbedarf haben.
- When light passes from air into glass it bends A. away from the normal and speeds up B. towards the normal and slows down C. towards the normal and speeds up D. along the surface Answer: B
- A glass has refractive index 1.5. Light travels in it at (speed in air = 3.0 x 10^8 m/s) A. 4.5 x 10^8 m/s B. 3.0 x 10^8 m/s C. 2.0 x 10^8 m/s D. 1.5 x 10^8 m/s Answer: C
- The critical angle of a material of refractive index 2.0 is closest to (sin c = 1/n) A. 24 degrees B. 30 degrees C. 42 degrees D. 60 degrees Answer: B
- An object placed beyond 2F from a converging lens forms an image that is A. virtual, upright, enlarged B. real, inverted, diminished C. real, upright, same size D. virtual, inverted, enlarged Answer: B
- Which colour of the visible spectrum is refracted the most by a prism? A. red B. yellow C. green D. violet Answer: D
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Lehrbuchabschnitt
Lenses
Describe and predict image formation and magnification as a consequence of refraction through convex and concave lenses, use ray diagrams to confirm image formation, and discuss how these properties of lenses determine their applications
"Physics: Lenses" by OpenStax, OpenStax, Rice University, licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Source: https://openstax.org/books/physics/pages/16-3-lenses. Access for free at https://openstax.org/books/physics/pages/1-introduction
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Lehrbuchabschnitt
Refraction
Explain refraction at media boundaries, predict the path of light after passing through a boundary (Snell’s law), describe the index of refraction of materials, explain total internal reflection, and describe applications of refraction and total internal reflection
"Physics: Refraction" by OpenStax, OpenStax, Rice University, licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Source: https://openstax.org/books/physics/pages/16-2-refraction. Access for free at https://openstax.org/books/physics/pages/1-introduction
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Übungsklausuren üben
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