Welcome to your Digital Sensors: Size Matters

1. The size of a "full frame" sensor is:
A cropped sensor:
When using a cropped sensor with a multiplication factor of 1.6 and a 100mm lens, what is the effective focal length of the lens?
When using a cropped sensor with a multiplication factor of 1.6 and a 28mm lens, what is the effective focal length of the lens?
Which lens would best resemble a 28mm lens when used on a camera with a cropped sensor that has a multiplication factor of 1.6?
What would you need to know in order to determine the effective focal length of a lens on a camera with a cropped sensor?