Welcome to Laser Pointer Forums! If you are looking for a laser you may want to check out the database of laser pointer companies. The link will open in a new window for your convenience.

 Laser Pointer Forums - Discuss Laser Pointers Physics Coursework On Lenses- Please help me! Laser Pointer Company Database     Laser Top Sites List     Lasers by Type     Green Lasers

03-08-2010, 10:11 PM #1
 Class 2M Laser Join Date: Jan 2010 Location: London, England Posts: 973 Rep Power: 29
JaiNobeZ
Class 2M Laser

Join Date: Jan 2010
Location: London, England
Posts: 973
Rep Power: 29

Alright. I'm doing a peice of Physics Coursework for my A-Level. It's worth 40/300 marks so it's quite important and I need some help, and probably will throughout the process of writing it so I'm starting this thread.

Every time I encounter a problem I'll post it in here and hope (possibly in vain, but hopefully not) that someone will come to my aid. Alternatively, If there's anyone nice enough to let me PM them when I run into trouble that would be much appreciated.

The coursework is mainly on Quality of Measurement and our ability to assess error margins & such. Nasty stuff. But we've got to show off our knowledge of Physics at the same time. Mine is on using three different methods to find the focal point of a lens. If anyone's really interested I'll post more info.

My first problem is that i know the equation 1/F = 1/V - 1/U when V is the Image distance (distance from the lens to the screen) and U is the Object distance (distance from the object to the lens), but I don't understand WHY. My textbook is pretty much useless.

So can anyone explain why 1/F = 1/V - 1/U?

Thanks in advance. You're all really helpful and I'll repay one day sooner or later if i can. Maybe by donating, or maybe by helping to aid the collective knowledge contained on the forum.

tl;dr Why does 1/F = 1/V - 1/U?

Last edited by JaiNobeZ; 03-08-2010 at 10:15 PM.

03-08-2010, 10:14 PM #2
 Class 2M Laser Join Date: Jan 2010 Location: London, England Posts: 973 Rep Power: 29
JaiNobeZ
Class 2M Laser

Join Date: Jan 2010
Location: London, England
Posts: 973
Rep Power: 29

Wow... reading through all that I realise I talk a lot of crap. Lol...

03-10-2010, 06:33 AM #3
 Class 3B Laser Join Date: Jan 2009 Location: Spain, tarragona Posts: 3,637 Rep Power: 218
Hallucynogenyc
Class 3B Laser

Join Date: Jan 2009
Location: Spain, tarragona
Posts: 3,637
Rep Power: 218

Optics Bench

Lurk a bit there. I can't explain you why just as I can't explain you why p=ma (is the Newton second law spelled like this in English?), they are just "laws"
__________________
The difference between an ignorant and a wise is that the wise knows the limits of his knowledge while the ignorant ignores the limits of his ignorance.
Learn how to use Opera and tell me about your experience here!

Wicked Lasers Evolution Pro 130mW ------------------> Review
Rayfoss 150mW waterproof
Rayfoss 200mW focusable torch -----------------------> Review
Dealextreme 5mW true laser pointer
Dealextreme 50mW true laser pointer
Dealextreme 100mW true laser pointer
Laserlands 30mW disco laser --------------------------> Review
5mW pointers (many of them)
DX 200mW Red laser (Dilda) --------------------------> Review
120mW PHR custom build
200mW GGW custom build

Focalprice 7\$ green&bluray laser goggles
Dealextreme tripod and clamp for laser holding -----> Review
DIY 3 motor Spirograph --------------------------------> Review
HLPM-2 laser power meter

03-10-2010, 07:18 AM #4
 Member Join Date: Feb 2010 Location: Cape Cod Massachusetts Posts: 43 Rep Power: 0
JIMS19
Member

Join Date: Feb 2010
Location: Cape Cod Massachusetts
Posts: 43
Rep Power: 0

Dear JaiNobe,I learned in school D=1/f. Thats diopters or lens power,thats D and the inverse of the focal length f divided by 1.Example a 4 meter focal length divided into 1=0.25 Dioptric power of the lens or a "quarter diopter lens"- I hope I helped some.

03-10-2010, 09:31 AM #5
 Class 3R Laser Join Date: Jan 2009 Location: United Kingdom Posts: 1,627 Rep Power: 63
Asherz
Class 3R Laser

Join Date: Jan 2009
Location: United Kingdom
Posts: 1,627
Rep Power: 63

Quote:
 Originally Posted by Hallucynogenyc Optics Bench Lurk a bit there. I can't explain you why just as I can't explain you why p=ma (is the Newton second law spelled like this in English?), they are just "laws"
In English I think it's F=ma

f = force
__________________
- 150mW Ehgemus Mini-RPL Review -

Collection of the Best Free games

445nm Custom build@1A - Old style Dorcy Jr. + purple anodized heatsink
Dino Direct 50mW Flashlight unit
DX True green 100mW
O-like module @ 171mW in Mini-RPL host
Single-line Argon @ 52mW 488nm Peak
PHR-803T @ 110mA in Jayrob MXDL host
DX Red 660nm 200mW
Dragon lasers 190nm-548nm Safety Goggles

 Thread Tools Display Modes Linear Mode

 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 OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

All times are GMT. The time now is 02:52 PM.

 -- DarkShadows V5 -- Responsive LPF -2562016 -- Default Style Contact Us - Laser Pointer Forums - Archive - Top