Come up with a procedure to determine focal length of lenses, one converging and
ID: 2300992 • Letter: C
Question
Come up with a procedure to determine focal length of lenses, one converging and one diverging.
Some equipment used for this: 2 lenses listed above, a light source, a screen, holders for optical devices, a dynamics track optical bench, and a ruler.
Please give a very detailed method of how you would do this. I have to understand this really well for the upcoming exam in 2 weeks and I am having a really hard time. Any pictures would be a bonus if there were any. I have absolutely no procedure to use - I have to make it up myself. Please help guide me through this so I can pass my class!!! I really appreciate your help! Please explain as detailed as possible because I care a lot about my grade and understanding the material. Just giving a brief answer won't help me learn. Thanks again so much!!!
Explanation / Answer
converging lense :
a simple metgod is distant object method.
place the convering lense at a large distance from source of light.
behind the lense keep the screen. move the scree until you get a bright image on the screen.
whenever you get bright image on the screen measure the distance between lense and screen.
This diatnce is the focal length.
we know
1/u + 1/v = 1/f
here, u = infinite (large distance)
1/infinite + 1/v = 1/f
1/v = 1/f ==> v = f
Diveverging lense :
Diverging lense produces a virtual image of real object and real image of virtual object.
in order to produce a virtual object we use converging lense.
we place the light source in between focal point and converging lense.
then we get a virtual image
1/u1 + 1/v1 = 1/f1
==> 1/v1 = 1/f1 - 1/u1
v1 = (u1-f1)/(u1*f1)
here u1<f1 so, v1 is negative(virtual)
now we place diverging lense behind the converging lense at a distance d.
now image distance for diverging lense is
u2 = (-v1+d) ("-"sign indicates virtual object)
now behind the diverging lense screen is placed.
we move the screen untill we get a bright image on the screen.
whenver we get image on the screen measure distance from diverging lense to screen
this distance is v2
now use the formula
1/u2 + 1/v2 = 1/f2
f2 = (v2-u2)/(v2*u2)