2 Fig. 2.1 shows a block of wood.
5.0 cm
5.0 cm
10.0 cm
Fig. 2.1 (not to scale)
(a) A student measures the mass of the block. He then measures the length of each side, as
shown in Fig. 2.1.
State the names of the measuring instruments used by the student.
1. ...?
2?
[2]

the diagram which shows forces as either balanced = same speed or unbalanced = accelerarting

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.