Light, mirrors and lensesIB MYP Physics: Subtopic test

1. 1
   A group of students build a pinhole camera from a cardboard tube. One end is closed with foil that has a tiny hole in the middle, and the other end is covered with tracing paper that acts as a screen. They point the hole at a lit candle in a dark room and see an image of the flame on the screen.

   (a)

   Which statement correctly describes the image on the screen?

   [1 mark]

   • AUpright and virtual
   • BUpright and real
   • CInverted and virtual
   • DInverted and real

   (b)

   Which fact about light explains how the image forms in the pinhole camera?

   [1 mark]

   • ALight is a longitudinal wave
   • BLight needs a medium to travel
   • CLight travels in straight lines
   • DLight travels at 3 × 10⁸ m/s in glass

   (c)

   The students move the camera closer to the candle. State what happens to the size of the image and explain why.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   Amira is short-sighted. Light from distant objects is focused in front of her retina, so distant objects look blurred, and she wears glasses to correct this. Her brother Idris is long-sighted, and he uses a magnifying glass to read the small print on medicine packets.

   (a)

   Which type of lens in Amira's glasses will correct her short sight?

   [1 mark]

   • AA converging lens
   • BA diverging lens
   • CA pinhole in a card
   • DA flat sheet of glass

   (b)

   Which statement describes the image formed on the retina by the lens of a healthy eye?

   [1 mark]

   • AReal, inverted and smaller than the object
   • BVirtual, upright and smaller than the object
   • CReal, upright and larger than the object
   • DVirtual, inverted and larger than the object

   (c)

   State the type of lens in Idris's magnifying glass and describe the image he sees.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student investigates how the shape of a converging lens affects its focal length. She holds each lens so that light from a distant window passes through it, then moves a white card behind the lens until a sharp image of the window forms. She measures the distance from the lens to the card. Lens P is thin and only slightly curved, lens Q is thicker, and lens R is the thickest and most strongly curved. Her results are 30 cm for P, 15 cm for Q and 6 cm for R.

   (a)

   Identify the independent variable, the dependent variable and one control variable in this investigation.

   [3 marks]

   (b)

   Describe the trend in the results and explain it. Explain why a distant window was used.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A charity supplies low-cost glasses to schoolchildren in rural areas where there are no opticians. Many children cannot read the board because some are short-sighted and some are long-sighted. The plastic lenses cost about 2 US dollars a pair and are made in a few standard strengths, chosen with a simple chart test run by trained teachers. The lenses scratch easily.

   (a)

   Explain how glasses can correct short sight and long sight.

   [6 marks]

   (b)

   Discuss and evaluate whether the charity's glasses programme is a good way to help the children.

   [6 marks]

   Total for question 4: 12 marks

End of questions