A camera has a 5 cm focal length. How far must the film be from the lens for a clear image of an object which is 25.4 cm away?
Answers
Answer:
Explanation:
Diameter of the circular sheet is 28 cm.
Radius =14 cm
Circumference of semicircular sheet =14π cm
Now the semicircular sheet is bent into an open circular cup.
Slant height of conical cup =l= radius of circular sheet =14 cm
Circumference of the base of conical cup = Circumference of semicircle sheet = πr=14π (∵R=7 cm)
Depth of conical cup = Height of cone =h=
l
2
−r
2
=
(14)
2
−(7)
2
=
196−49
=
147
=7
3
cm
Capacity of the conical cup =
3
1
πR
2
h
=
3
1
×
7
22
×7
2
×7
3
=
3
1078
3
cm
3