Everything Science Grade 11

13.2 CHAPTER 13. GEOMETRICAL OPTICS

is greater than 2 f and adjust the positionof the screen until a sharp focused image is

obtained. Note that there are two positions forwhich a sharp focusedimage will not

be obtained on the screen. When this is so, remove the screen and look at the candle

through the lens.

3. Fill in the relevant information on the table below
   Results:

Relative position

of object

Relative position

of image

Image upright

or inverted

Relative size

of image

Nature of

image

Beyond 2 f

cm

At 2 f

cm

Between 2 f andf

cm

Atf

cm

Betweenf and the

lens

cm

QUESTIONS:

1. When a convex lensis being used:
   (a) A real inverted image is formed when an object is placed
   (b) No image is formedwhen an object is placed
   (c) An upright, enlarged, virtual image is formedwhen an object is placed


2. Write a conclusion for this investigation.

Activity: Lenses C

Aim:

To determine the mathematical relationship between d 0 , diand f for a lens.

Method:

1. Using the same arrangement as in Experiment Lenses B, place the object (candle) at the
   distance indicated fromthe lens.


2. Move the screen until a clear sharp image isobtained. Record the results on the table
   below.
   Results:
   f = focal length of lens
   d 0 = object distance
   di= image distance

Object distance Image distance d^10 d^1 i d^10 +d^1 i

d 0 (cm) di(cm) (cm−^1 ) (cm−^1 ) (cm−^1 )

25,0

20,0

18,0

15,0

Average =

Reciprocal of average =

�

1

1

d 0 +

1

di

�

= (a)

Focal length of lens = (b)