Physics - 14 Light - Required Practical 9: Light

Aims:

  • identify and investigate incident, reflected and refracted rays of light

Risk Assessment:

  • sharp edges on glass blocks

  • chips from glass blocks

  • ray boxes may get hot

Safety:

  • be careful when handling glass blocks - do not touch the edges, and do not bump them together

  • be careful when touching the ray box, and allow it to cool down

Equipment:

  • clear acrylic block

  • clear glass block

  • ray box with slit

  • protractor

  • ruler

  • pencil

  • large (A4 or A3), plain sheets of paper

Control variables:

  • (if investigating changes due to material) angle of incidence

  • (if investigating changes due to angle of incidence) material

Independent variable:

  • (if investigating changes due to angle of incidence) angle of incidence

  • (if investigating changes due to angle of incidence) material

Dependent variable:

  • angle of refraction OR angle of reflection

Method:

Activity 1: investigating refraction

  1. Place the glass block on a plain piece of paper and draw around it carefully with the pencil

  2. Angle the ray box so that a ray of light travels into the block at one side and out from the other. Draw at least two crosses on the paper using pencil both for the ray entering and the ray leaving the block. Also mark the place on the edge of the block where the rays enter and exit

  3. Remove the block and switch off the ray box to allow it to cool. Use the ruler to connect the crosses, as well as connecting the two rays where the block had been. Add arrows to show the direction of the light

  4. Use the protractor, pencil and ruler to draw normal lines perpendicular to the block’s edges, where the rays had intersected the block’s edge

  5. Label the angles of incidence and refraction, and measure them with the protractor, recording the results in a table

  6. Repeat steps 1-5 either with blocks of different materials or with difference angles of incidence

Activity 2: investigating reflection

  1. Place the glass block on a plain piece of paper and draw around it carefully with the pencil

  2. Angle the ray box so that a ray of light travels towards the block, and then away from it. Draw at least two crosses on the paper using pencil both for the ray travelling towards the block and the ray travelling away from it. Also mark the place on the edge of the block where the rays meet it

  3. Remove the block and switch off the ray box to allow it to cool. Use the ruler to connect the crosses. Add arrows to show the direction of the light

  4. Use the protractor, pencil and ruler to draw a normal line perpendicular to the block’s edge, where the rays had intersected the block’s edge

  5. Label the angles of incidence and reflection, and measure them with the protractor, recording the results in a table

  6. Repeat steps 1-5 either with blocks of different materials or with difference angles of incidence