If the focal length of a camera is 20cm, the distance from the film at which the lens must be set to produce a sharp image of 100cm away is

Okogbaba

7 years ago

Wrong
F=20
U=?
V=100
1/f=1/v+1/u
1/20=1/100+1/u
1/u=1/20-1/100
1/u=4/100
U=25

Valentineezekiel

3 years ago

My school the selected answer is wrong😑please make necessary corrections...

C is absolutely correct🔥🔥🤝🤝
u=?
v=100cm
f=20cm
where u=object distance
v=image distance
f=focal length
using the lens formula
1/f=1/u+1/v
making u the subject of formula
1/u=1/f-1/v
1/u =1/20-1/100
1/u=5-1/100
1/u=4/100
u=100/4
u=25cm🔥🔥🔥

OG_Loc

3 years ago

@myschool blessing, paul and the likes please y'all review the answer to this question.
the answer is 25cm

s.samuel

3 years ago

Actually I think the answer is correct because v= image distance or height of image
U = object distance or height of object
The distance between the film and the lens = distance of image from the lens( if you study the image of a camera well you will understand)
The question said find v (image distance)
The distance between lens and film = image distance
Because LENS is the mouth of the camera and FILM is the end of the camera were the image is formed

I. e means v=100
(study diagram of a camera well and you will understand)

If you don't get the explanation am sorry
I wish I could make a video to explain

FeSage19

3 years ago

Please review your answer, the answer should be 25cm

Tochibaby

1 year ago

my school please I don't understand how you got the answer to question 79 physics 2018

Chikamiracle

7 years ago

my school the ans is D =25

AlphyJaycob555

2 months ago

Most options I choose are been changed to the wrong one 😞
pls I'm very discouraged,pls do something about it 🙏