It’s also possible to buy a teleconverter, which increases the focal length of an existing lens (like a magnifying glass would).
It’s also possible to buy a teleconverter, which increases the focal length of an existing lens (like a magnifying glass would). However it will reduce the aperture by at least one stop (so if your lens normally goes as low as f/3, you’ll only be able to shoot at f/4 or higher).