Two lenses of focal length 4.5cm and 1.5cm are placed at a certain distance apart, calculate the distance between the lenses if they form an achromatic combination

3.0cm

For lenses in an achromatic combination, the following condition holds, assuming the two lenses are of the same materials;

d =     ---------(i)

Where;

d= distance between lenses

f₁ = focal length of the first lens

f₂ = focal length of the second lens

From the question;

f₁ = 4.5cm

f₂ = 1.5cm

Substitute these values into equation (i) as follows;

d =

d =

d = 3.0cm

Therefore, the distance between the two lenses is 3.0cm

snell's law

refractve index = sin incidence / sin refraction