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Topic 8 Practice Paper: Light — question paper

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QQ/IGCSE-PHYS/T8

IGCSE · Cambridge IGCSE Physics (Extended (Core + Supplement))

Topic 8 Practice Paper

Light

Duration: 40 minutes
Total: 30 marks
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Class:
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Date:

READ THESE INSTRUCTIONS FIRST

  • Answer all questions.
  • Section A contains ten multiple-choice questions. Choose one answer, A, B, C or D, for each.
  • Section B contains structured questions. Write your answers in the spaces provided.
  • The number of marks is given in brackets [ ] at the end of each question or part question.
  • The total mark for this paper is 30.

Original practice material written against the Cambridge IGCSE Physics syllabus. It is not an official Cambridge examination paper. Topic 8: Light (reflection, refraction, critical angle and TIR, lenses, dispersion).

For Examiner’s Use
Section A/ 10
Section B/ 20
Total/ 30

Section A: Multiple-choice questions[10 marks]

Choose one answer for each question. Each question is worth 1 mark.

  1. 1

    A ray strikes a plane mirror at 20° to the mirror’s surface. The angle of reflection is

    1. A70°
    2. B20°
    3. C40°
    4. D10°
    ( )
  2. 2

    Which description of a plane mirror image is correct?

    1. AVirtual, diminished, behind the mirror
    2. BReal, same size, in front of the mirror
    3. CVirtual, same size, same distance behind as the object is in front
    4. DReal, inverted, same distance behind
    ( )
  3. 3

    Light crosses from glass into air at an angle. It bends

    1. Atowards the normal, because it slows down
    2. Baway from the normal, because it speeds up
    3. Ctowards the normal, because it speeds up
    4. Dalong the normal always
    ( )
  4. 4

    The critical angle for a glass–air boundary is 42°. A ray inside the glass hits the boundary at 50°. The ray is

    1. Arefracted towards the normal
    2. Brefracted along the surface
    3. Cabsorbed by the glass
    4. Dtotally internally reflected
    ( )
  5. 5

    A medium has a critical angle of 45°. Its refractive index is

    1. A1.41
    2. B0.71
    3. C1.00
    4. D2.00
    ( )
  6. 6

    Optical fibres carry light over long distances using

    1. Arefraction out of the fibre at each bend
    2. Bthe light travelling along a metal wire inside
    3. Ctotal internal reflection at the fibre wall
    4. Dechoes of sound inside the fibre
    ( )
  7. 7

    A thin diverging lens acting on a parallel beam of light makes the rays

    1. Across at a point behind the lens
    2. Bspread as if coming from a principal focus in front of the lens
    3. Ccome to a focus in front of the lens
    4. Dcontinue parallel but closer together
    ( )
  8. 8

    An object inside the focal length of a converging lens produces an image that is

    1. Ainverted and real
    2. Binverted and virtual
    3. Cdiminished and real
    4. Dupright, enlarged and virtual
    ( )
  9. 9

    White light passes through a glass prism and spreads into a spectrum. The colour refracted the least is

    1. Ared
    2. Bgreen
    3. Cviolet
    4. Dyellow
    ( )
  10. 10

    A ray in air meets a glass block with an angle of incidence of 0° (along the normal). Inside the glass the ray

    1. Abends strongly towards the normal
    2. Bcontinues along the normal without bending
    3. Cbends away from the normal
    4. Dis totally internally reflected
    ( )

Section B: Structured questions[20 marks]

Answer all questions in the spaces provided.

  1. 11

    A small torch stands 6.0 cm in front of a plane mirror. A ray from the torch strikes the mirror at 35° to the normal.

    1. (a)

      State the angle of reflection and justify it with the law of reflection.

      [2]
    2. (b)

      State the position of the image of the torch.

      [1]
    3. (c)

      Describe how the reflected rays appear to a person looking into the mirror, and name the type of image.

      [2]
  2. 12

    A student traces a ray through a semicircular glass block on a sheet of paper, marking the entry and exit points, then draws the path with the block removed.

    1. (a)

      State what happens to the direction of the ray as it enters the flat face of the block from air.

      [1]
    2. (b)

      The measured angles are i = 40°, r = 25°. Calculate the refractive index of the glass.

      [2]
    3. (c)

      Use your refractive index to find the angle beyond which light hitting the glass–air face is totally internally reflected.

      [2]
    4. (d)

      State the one condition, besides the angle, needed for total internal reflection at the glass–air boundary.

      [1]
  3. 13

    A converging lens has a focal length of 5.0 cm. It is used as a magnifying glass to read a stamp.

    1. (a)

      State the maximum distance the stamp may be held from the lens for the lens to magnify it.

      [1]
    2. (b)

      State the size, attitude and type of the image seen through the lens.

      [3]
    3. (c)

      The image cannot be caught on a screen. Explain why.

      [1]
  4. 14

    A beam of white light passes through a narrow slit and then through a glass prism, and a spectrum is seen on a screen.

    1. (a)

      Name the effect that splits the white light, and state what causes it.

      [2]
    2. (b)

      State the colour at the top of the spectrum (refracted least) and the colour at the bottom (refracted most).

      [1]
    3. (c)

      The slit is replaced by a source emitting only one frequency of green light. State what is now seen on the screen and name this kind of light.

      [1]

— End of paper —