What is the focal length of a lens

The focal length of a lens is the distance between the lens and the image sensor when the subject is in focus, usually stated in millimeters.

this is refering to a camera lens, not glasses and what not, glasses do not have a focus length, only equipment that has the ability to focus

Explanation:

May I have brainliest please? :)

b would be the answer

here we know that ball will drop down by total distance 3.2 m

so here we know that

now using kinematics

now in the same time it will cover horizontal distance of 0.75 m

so speed of the ball will be