Question

An object is 25 cm away from a convex len.The height of the image is twice the height of the object.Find it's focal length.

Answer 1

@Abhisar

Answer 2

Ok, I am gonna tell you a Super Formula for lens

\(\sf \boxed{M=\frac{V}{U}=\frac{f}{f+u}=\frac{f-v}{f}=\frac{h_i}{h_o}}\)

Answer 3

M= magnification,
V=image distance
u=object distance
f=focal length
\(\sf h_i~and~h_o\) are image and object height respectively.

Answer 4

Note: You need to follow the cartasian coordinate.

Answer 5

Never heard of that :/

Answer 6

Heard of what?
Cartasian cordinate

Answer 7

Never heard of this Cartasian cordinate

Answer 8

Do you know about the sign convension?

Answer 9

To be honest,I don't know a thing about Optics...

Answer 10

Ok, why don't you read this
http://www.st-andrews.ac.uk/~bds2/optics/cartesian.html

Answer 11

Done.

Answer 12

How do I solve this problem?

Answer 13

Use the formula m = f/f+u

Answer 14

M is magnification. Because the height of the image is twice that of object so the magnification will be 2

Answer 15

You need to plug in the values with appropriate sign. that's it

2=f/f+ (-25)

Answer 16

-50 cm?

Answer 17

Re-check it should be in positive value

Answer 18

50 cm?

Answer 19

Yes.

Answer 20

Thanks

Answer 21

Welcome c: