Paper 2 Required Practicals

Question 1

How do we Investigate the reflection of light by different types of surfaces and refraction of light by different substances.

Answer 1

1. You need a ray box, lens and slit which will produce a narrow raw of light.
   Remember to switch ray boxes off when you are not using them.
   This can also be done using a dangerous laser.
2. Then draw a straight line down an A3 piece of paper using a ruler
3. Then use a protractor to draw a line at right angles. This is the normal.
4. Then place a glass block against the first line so that the normal is near the centre of the block.
   Draw around the glass block
   Make sure you turn off all the lights
5. Then use the ray box to direct a ray of light so it hits the block at the normal. This is the incident Ray.
6. Then we adjust the ray box to change the angle of incidence.
   At a certain angle, we can see a ray reflect from the surface of the block.
7. We can also see another ray leaving the block from the opposite side. This is the transmitted ray.
8. Then mark the path of the incident ray and reflected ray and the transmitted ray with crosses.
9. Then turn on the room lights and switch off the ray box.
   Then remove the glass block.
10. Draw in all the rays and make sure to draw the path of the transmitted ray through the glass block.
    Use a protractor to measure the angles of incidence, Reflection and refraction.
11. Then repeat the experiment with different material such as Perspex.

However the angle of refraction will be different with Perspex than with glass.
That is because the angle of refraction is different for different materials. Due to their density?

Question 2

Required practical activity 9: investigate the reflection of light by different types of surface and the refraction of light by different substances.

Answer 2

1. Set up a ray box, slit and lens so that a narrow ray of light is produced.
2. Place a 30 centimetre (cm) ruler near the middle of a piece of plain A3 paper. Draw a straight line parallel to its longer sides. Use a protractor to draw a second line at right angles to this line. Label this line with an ‘N’ for ‘normal’.
3. Place the longest side of a rectangular acrylic polymer block against the first line. With the normal near the middle of the block, carefully draw around the block without moving it.
4. Use the ray box to shine a ray of light at the point where the normal meets the block. This is the incident ray.
5. The angle between the normal and the incident ray is called the angle of incidence. Move the ray box or paper to change the angle of incidence. The aim is to see a clear ray reflected from the surface of the block and another clear ray leaving the opposite face of the block.
6. Using a pencil on the paper, mark the path of:
   
   • the incident ray with a cross
   • the reflected ray with a cross
   • the ray that leaves the block with two crosses - one near the block and the other further away
7. Remove the block. Join the crosses to show the paths of the light rays.
8. Repeat steps 2 to 7 for a rectangular glass block.
9. Measure the angle of incidence, angle of refraction and angle of reflection for each block.

Question 3

Required practical activity 9: investigate the reflection of light by different types of surface and the refraction of light by different substances.

Safety considerations and Hazards

Answer 3

Evaluating the Experiment

Systematic Errors:

• An error could occur if the 90° lines are drawn incorrectly
  
  • Use a set square to draw perpendicular lines
• If the mirror is distorted, this could affect the reflection angle, so make sure there are little to no blemishes on it

[popover id=”QzmzrDGuwfpwthVl” label=”Random Errors:]

• The points for the incoming and reflected beam may be inaccurately marked
  
  • Use a sharpened pencil and mark in the middle of the beam
• The protractor resolution may make it difficult to read the angles accurately
  
  • Use a protractor with a higher resolution

Safety Considerations

• The ray box light could cause burns if touched
  
  • Run burns under cold running water for at least five minute
• Looking directly into the light may damage the eyes
  
  • Avoid looking directly at the light
  • Stand behind the ray box during the experiment
• Keep all liquids away from the electrical equipment and paper
• Take care using the mirror
  
  • Damages on the mirror can affect the outcome of the reflection experiment