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Year 11 - Science

Convex lenses

Electromagnetic waves

Unit Summary

This unit explores reflection, refraction, and lenses using ray diagrams. It covers the electromagnetic spectrum, light as a wave, absorption, transmission, and practical uses. Emphasis is on risks, temperature balance, data presentation, and unit conversions.

Lesson Summary

You will learn to use a convex lens to form an image on a screen, and describe how the image can vary depending on the object distance.

Key Notes

  • Convex lenses can produce an inverted image on a screen by refracting light.
  • Rays parallel to the principal axis are refracted to the principal focus, located at the focal length of a convex lens.
  • The image distance and size (magnification) depend on the power of the lens and the object distance.
  • As the object distance decreases, the image distance and size both increase, until the object reaches the focal length.
  • If the object is too close to the lens, the rays leaving the lens are parallel/diverging, images can't form on a screen.

Vocabulary To Learn

  • diminished: Diminished means smaller than an object's real size. It is the opposite of magnified.
  • convex: A convex shape bulges 'out' rather than bulging 'in' (concave).
  • principal focus: Rays of light incident on a convex lens parallel to the principal axis are focused to a point called the principal focus.
  • focal length: The focal length is the distance from the centre of the lens to the principal focus.
  • lens power: The greater the power of a lens, the greater the angles through which light is refracted and the shorter the focal length.

Common Mistakes To Avoid

  • Pupils often think there is only one ray of light for each point of light on the image.

3 Quick Questions (With Answers)

1. Explain the scientific idea in this lesson using two key points.

Convex lenses can produce an inverted image on a screen by refracting light. Rays parallel to the principal axis are refracted to the principal focus, located at the focal length of a convex lens.

2. Define this scientific word and use it in context. 'diminished'

Diminished means smaller than an object's real size. It is the opposite of magnified. Include the word in a full scientific explanation, not as a single label.

3. Correct this common scientific misunderstanding.

Mistake: Pupils often think there is only one ray of light for each point of light on the image. Correction: Teach explicitly about many rays of light from each point on an object being brought together to form a bright spot on the image.

More Lessons In This Unit

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