Answer:
Actual focal spot-
Step-by-step explanation:
Actual focal spot-
it is referred to that spot of focal where beam of electron converge to one place.
focal sopt size for different process are
1) for mammography - 0.3 mm to 0.6 mm
2) for radiography - 1.00 to 1.2 mm
Focal length of focal spot can be calculated by using following relation

where
is angle of anode