Photographic film in cameras is manufactured to be sensitive to the same range of wavelengths as our eyes are. There are some films made to be sensitive to different types of light waves including infrared film. In order for the film to be exposed properly in a camera a couple things must happen. First the shutter should open at an appropriate speed, the aperture should be open to an appropriate width, and lens should be focused. For now we'll only talk about the shutter and aperture.
Shutters control the amount of light by the length of time they remain open to expose the film.
If the shutter is not open long enough, the film will be underexposed and create a light image. In vice, if the shutter is open too long, the film will be overexposed and create a dark image. Neither of which is desirable for your photo. On your camera you can control the amount of time the shutter will remain open with the guidance of a light meter to test your lighting and then changing your shutter-speed dial to the suggested amount of time. The speed of the shutter is measured by seconds, starting with 1 second and moving faster at half the next setting or slower at twice the following setting.