1. 1
   A student is investigating reflection using a plane mirror fixed upright on a bench. A ray of light from a ray box is directed at the mirror at a shallow angle, and the student measures the angles the incident and reflected rays make with the mirror surface using a protractor placed flat on the bench.

   (a)

   A ray of light travels through air and strikes a flat mirror. The ray makes an angle of 35° with the mirror surface itself, not with the normal. Which statement about the reflected ray is correct?

   [1 mark]

   • AThe angle of reflection, measured from the normal, is 55°
   • BThe angle of reflection, measured from the normal, is 35°
   • CThe angle of reflection, measured from the mirror surface, is 90°
   • DThe reflected ray travels back along the same path as the incident ray

   (b)

   The student then covers the mirror with a rough, matte white surface instead and repeats the experiment, shining the same ray box at it from several different angles. Which statement best describes what happens to parallel rays of light striking this rough surface?

   [1 mark]

   • AAll the reflected rays remain parallel to each other, as with the mirror
   • BThe reflected rays scatter in many different directions because the surface is uneven at a small scale
   • CNo light is reflected because the surface absorbs it completely
   • DThe light passes straight through the rough surface

   (c)

   State the law of reflection, and explain why the smooth mirror produces a clear image of the ray box while the rough white surface does not.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A technician shines a laser into a semi-circular glass block from inside the glass, aiming the ray at the flat, curved-side boundary between the glass and the surrounding air so that it always meets the boundary at the centre of the flat face. She gradually increases the angle at which the laser strikes this boundary, measured from the normal, and observes the effect on the ray leaving the glass block and on any ray reflected back inside the block.

   (a)

   As the technician increases the angle of incidence inside the glass block, the refracted ray in the air bends further away from the normal until, at a certain angle, the refracted ray travels along the boundary itself (at 90° to the normal). What is this specific angle of incidence called?

   [1 mark]

   • AThe angle of reflection
   • BThe angle of refraction
   • CThe critical angle
   • DThe normal angle

   (b)

   The technician now increases the angle of incidence beyond the critical angle. What happens to the light ray at the boundary?

   [1 mark]

   • AIt refracts out of the glass at an angle greater than 90° from the normal
   • BIt stops travelling and is absorbed at the boundary
   • CIt splits equally between refraction into the air and reflection into the glass, as at smaller angles
   • DIt undergoes total internal reflection, with all the light reflected back into the glass

   (c)

   Explain, in terms of the change in the speed of light, why the ray refracts and bends away from the normal as it passes from the glass into the air at angles below the critical angle.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A pottery shop sells mugs with different coloured glazes. A customer is examining a mug with a blue glaze under the shop's white fluorescent lighting. The shop assistant explains that if the customer instead views the mug through a red filter held between her eye and the mug, the mug will look very different.

   (a)

   The customer notices that the blue mug looks blue in white light. Explain, in terms of absorption and reflection of light, why the mug appears blue.

   [3 marks]

   (b)

   The assistant is correct that viewing the blue mug through a red filter makes it appear almost black. Explain, in terms of transmission and absorption of light by the filter, why this happens.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   An optician has two unlabelled lenses on her desk: one is thick and bulges outward at its centre, and the other is thin at its centre and bulges outward at its edges. She wants to explain to a trainee how each type of lens forms images, using an object placed close to the converging lens and another placed close to the diverging lens.

   (a)

   Describe how the shape of each lens determines whether it is a converging or diverging lens, and explain, in terms of the refraction of light rays, how each lens type affects a set of parallel rays of light passing through it.

   [6 marks]

   (b)

   The optician places a small object very close to the converging lens, closer than its principal focus, and then places an identical object close to the diverging lens. Explain, in terms of the type of image formed, the differences between the images produced by the two lenses in these situations, referring to whether each image is real or virtual and magnified or diminished.

   [6 marks]

   Total for question 4: 12 marks

End of questions