Uma Câmara escura de orifício com 15 cm de profundidade produz uma determinada imagem para um objeto situado a 10 m do orifício. Qual a profundidade de uma câmara escura que, colocada a 20 m do mesmo objeto e produz uma imagem igual ao dobro da anterior? a) ( ) 30 cm b) ( ) 7,5 m c) ( ) 7,5 cm d) ( ) 30 m e) ( ) 60 m

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.