Go Back   Science Forums Biology Forum Molecular Biology Forum Physics Chemistry Forum > General Science Forums > Physics Forum
Register Search Today's Posts Mark Forums Read

Physics Forum Physics Forum. Discuss and ask physics questions, kinematics and other physics problems.


Tough Question in Electo-Optics

Tough Question in Electo-Optics - Physics Forum

Tough Question in Electo-Optics - Physics Forum. Discuss and ask physics questions, kinematics and other physics problems.


Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 09-27-2004, 11:43 PM
Andrea Zammit
Guest
 
Posts: n/a
Default Tough Question in Electo-Optics





A converging lens held near a flashlight is used to put an image of the bulb
on a wall that is 1.60m from the lens. With the flashlight fixed, the lens
is moved closer to the wall and a sharp image is again formed when the lens
is 15cm from the wall.

a. What is the focal length of the lens?
b. How far is the flashlight bulb from the wall?

I cannot figure it out and am getting very frustrated. Any help would be
appreciated.

Colin



Reply With Quote
  #2  
Old 09-28-2004, 01:38 PM
tadchem
Guest
 
Posts: n/a
Default Tough Question in Electo-Optics

"Andrea Zammit" <[Only registered users see links. ]> wrote in message news:<EB16d.2998$[Only registered users see links. ]>...

The equation you need is here (equation 4):
[Only registered users see links. ]

in ASCII:

1/f = 1/So1 + 1/Si2

Draw a diagram:

source lens image
*------------()-----------|
So1 Si2
<------------B------------>

You actually have 2 cases here:
case I-

1/f = 1/(B-1.6) + 1/(1.6)

where Si2 = 1.6 meters, the distance from the lens to the image, and B
is the answer to part b, the distance from the light source to the
image.

case II-

1/f = 1/(B-0.15) + 1/(0.15)

where Si2 is now 0.15 meters

Are you up to the algebra of solving 2 equations in two unknowns?

HINT: 1/f = 1/(B-1.6) + 1/(1.6) = 1/(B-0.15) + 1/(0.15)


Tom Davidson
Richmond, VA
Reply With Quote
Reply

Tags
electooptics , question , tough


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Interview Question - Too Tough? Darren Rhodes Chemistry Forum 10 06-06-2013 04:34 PM
another question regarding optics please help? valerie Physics Forum 0 07-20-2009 04:20 PM
question from physical optics ? saman Physics Forum 0 06-27-2009 11:16 AM
metal optics, superluminal tunneling effects, spin formula in electrodynamics Josef Matz Forum Physik 0 03-31-2005 12:25 AM
Sub wavelength point light optics question Anth Physics Forum 3 06-03-2004 06:42 AM


All times are GMT. The time now is 04:50 PM.


Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright 2005 - 2012 Molecular Station | All Rights Reserved
Page generated in 0.12264 seconds with 16 queries