4. Dr. Sayer is studying how our perceptions of attractiveness have changed over time. He hypothesized that, due to increased concerns over skin cancer, tan skin is perceived as less attractive now than it was 20 years

ago. He compared data from 1987 to current data and found that, on average, tan skin was rated as 4.2 in

attractiveness (on a scale of 1-5, with 5 being most attractive) in 1987 as compared to 3.7 today. In

analyzing these results, what three factors must Dr. Sayer consider when determining if these averages are

reliable?

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.