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Grade 7 Science — Light, shadows and reflection

Tell luminous objects from non-luminous, use the straight-line rule to explain shadows, and give the four properties of an image in a plane mirror.

Name: ________________________

Before you start

A torch, an opaque object and a screen — the three parts of a shadow set-up.

1234
  1. 1. Torch
  2. 2. Object
  3. 3. Screen
  4. 4. Shadow

Take away any one of the three and there is nothing to see: no light, no object to block it, or no surface for the dark patch to land on. In everyday life a wall, a floor or the ground plays the part of the screen.

  1. 1.Raise your left hand at a plane mirror and the image seems to raise its right. This perceived left-right swap has a two-word name. What is it?

  2. 2.A shiny plate held in sunlight throws a bright patch onto a shaded wall, because it has changed the direction the light was traveling in. What is that change of direction called?

  3. 3.Why is the word AMBULANCE painted reversed across the front of an ambulance?

    • a) So that it looks different from ordinary vehicle lettering
    • b) So that it stays readable when the ambulance is moving fast
    • c) So that it reads the right way round in the rear-view mirror of the vehicle ahead
    • d) So that it can be read from a great distance

  4. 4.What three things do you need in order to see a shadow?

    • a) Sunlight, a colored object, and a dark room
    • b) A mirror, an opaque object, and a screen
    • c) A source of light, an opaque object, and a screen
    • d) A source of light, a transparent object, and a mirror

  5. 5.Which set of properties describes the image formed by a plane mirror?

    • a) Smaller than the object, erect, and obtainable on a screen
    • b) Larger than the object, upside down, and laterally inverted
    • c) Same size as the object, erect, laterally inverted, and not obtainable on a screen
    • d) Same size as the object, upside down, and obtainable on a screen

  6. 6.Sort each material by how much light gets through it.

    Groups: Transparent · Translucent · Opaque

    • Cardboard
    • Tracing paper
    • Thick cloth
    • Glass

  7. 7.Sort each of these by whether it gives out light of its own.

    Groups: Luminous · Non-luminous

    • Lightning
    • A mirror
    • The Pole Star
    • The Moon
    • A firefly
    • The Sun

  8. 8.Match each item to what it does.

    • A pinhole camera
    • An opaque object
    • A transparent object
    • A shadow
    • the dark region formed behind an object
    • blocks light completely
    • lets light pass almost completely through
    • forms an inverted image

Answer key — Grade 7 Science — Light, shadows and reflection

  1. 1. lateral inversion
  2. 2.
    • reflection
    • reflection of light
  3. 3. c) So that it reads the right way round in the rear-view mirror of the vehicle ahead
  4. 4. c) A source of light, an opaque object, and a screen
  5. 5. c) Same size as the object, erect, laterally inverted, and not obtainable on a screen
  6. 6. Glass → Transparent; Tracing paper → Translucent; Cardboard → Opaque; Thick cloth → Opaque
  7. 7. The Sun → Luminous; The Pole Star → Luminous; Lightning → Luminous; A firefly → Luminous; The Moon → Non-luminous; A mirror → Non-luminous
  8. 8. A pinhole camera → forms an inverted image; An opaque object → blocks light completely; A transparent object → lets light pass almost completely through; A shadow → the dark region formed behind an object