A certain slide projector has a lens of focal length 15 cm….

A certain slide projector has a lens of focal length 15 cm. This lens forms an image measuring 100 cm × 100 cm on the screen when a slide whose dimensions are 5 cm × 5 cm is being magnified. How far from the lens should the screen be placed? Express the answer in cm.

A 500-nm-wavelength beam of light illuminates a soap film wi…

A 500-nm-wavelength beam of light illuminates a soap film with air on both sides and an index of refraction 1.33. If the beam of light is incident normally on the film, what is the minimum thickness of the film to make the reflected light enhanced in brightness (constructive interference)? Express the answer in nanometers, nm.