A cooling curve for a certain mass of molten candle wax is given below. 55
50
45
Temperature (°C)
B
40
A
30
2
4
5
6
8 9
10 :
12
nts
13
15
Time (minutes)
(1) Why is the temperature on the graph constant between A and B?
(ii) Use the graph to find the melting point of candle wax.

the bal will not change its velocity.

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.