<< Chapter < Page Chapter >> Page >
A double convex lens is a converging lens.

[link] shows a convex lens. Light rays traveling through a convex lens are bent towards the principal axis. For this reason, convex lenses are called converging lenses.

Light rays bend towards each other or converge when they travel through a convex lens. F 1 and F 2 are the foci of the lens.

When an object is placed in front of a lens, the light rays coming from the object are refracted by the lens. An image of the object is produced at the point where the light rays intersect. The type of images created by a convex lens is dependent on the position of the object. We will examine the following cases:

  1. the object is placed at a distance greater than 2 f from the lens
  2. the object is placed at a distance equal to 2 f from the lens
  3. the object is placed at a distance between 2 f and f from the lens
  4. the object is placed at a distance less than f from the lens

We examine the properties of the image in each of these cases by drawing ray diagrams. We can find the image by tracing the path of three light rays through the lens. Any two of these rays will show us the location of the image. The third ray is used to check that the location is correct.

Experiment : lenses a

Aim:

To determine the focal length of a convex lens.

Method:

  1. Using a distant object from outside, adjust the position of the convex lens so that it gives the smallest possible focus on a sheet of paper that is held parallel to the lens.
  2. Measure the distance between the lens and the sheet of paper as accurately as possible.

Results:

The focal length of the lens is                       cm

Experiment : lenses b

Aim:

To investigate the position, size and nature of the image formed by a convex lens.

Method:

  1. Set up a candle, and the lens from Experiment Lenses A in its holder and the screen in a straight line on the metre rule. Make sure the lens holder is on the 50 cm mark. From your knowledge of the focal length of your lens, note where f and 2 f are on both sides of the lens.
  2. Using the position indicated on the table below, start with the candle at a position that is greater than 2 f and adjust the position of the screen until a sharp focused image is obtained. Note that there are two positions for which a sharp focused image 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
Experimental setup for investigation.

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 and f
        cm
At f
        cm
Between f and the lens
        cm

QUESTIONS:

  1. When a convex lens is being used:
    1. A real inverted image is formed when an object is placed                      
    2. No image is formed when an object is placed                      
    3. An upright, enlarged, virtual image is formed when an object is placed                      
  2. Write a conclusion for this investigation.

Experiment : lenses c

Aim:

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

Questions & Answers

during a snooker competition ,a 200g ball A m moving with velocity va collide head on with a identical ball B that was at rest.A after the collision ball A remains at rest wile ball B moves on with a velocity of 4m/s? With what speed was ball a moving before the collision
mathew Reply
a vector can be resolved into a horizontal component only
Lizoh Reply
how to calculate normal force
Chauke Reply
how to calculate wavelength
Lizoh
Hello. How does a real gas behave under low temperature and high pressure?
Valerie Reply
does a vector quantity include force and distance?
Lebo Reply
yes
Itumeleng
what's the difference between a vector and a scalar?
Keaobaka
vector is the physical quantity with magnitude and direction Scalar is the Physical quantity with magnitude only
Bobo
Newton's second law of motion
Thelma Reply
Newton second law motin
Shife
Newton's second law of motion: When a resultant/net force acts on an object, the object will accelerate in the direction of the force at an acceleration directly proportional to the force and inversely proportional to the mass of the object.
Bobo
newtons third law of motion
Ayakha
what is tail to tail method
Thobile Reply
a person was standing in a stationary lift / elevator and scale shown is 490N and then 470N when the lift started to move. Did the lift go up or down?
Kamva Reply
down
Fabzeey
How do you state snell's law
Mlondi Reply
The ratio of the sine of the angle of incidence in one medium to the sine of the angle of refraction in the other medium is constant
Boss
who was the first person to discover nuclears bomb
Ismael Reply
how to calculate resistance in grade 11
Ngomane Reply
last year memo in 2018 June exam
Ngomane
can I have last june question paper2
Mike
yes
Ismael
hello
Amanda
hello
Patricia
is there any physics e-copy textbooks?
Patricia
states the Newton's second law of motion
Shallin Reply
In words it says:" when a net force is applied to an object of mass, It accelerates in the direction of the net force. The acceleration is directly proportional to the net force and inversely proportional to the mass".
Buhle
And in symbols: Fnet = ma
Buhle
thank you
Shallin
pleasure
Buhle
hello everyone
Ngomane
hello
Mzondi
hlw
manu
which degree is usually be a refractive angle before it complete a totally reflection?
Mzondi
90°
Boss
yes obviously 90 degree
manu
fnet=ma
Fabzeey
how does hydrogen bonds differ from London force
Madzivha Reply
Hydrogen bonds are the strongest intermolecular forces and London forces are the weakest. Hydrogen bonds exist between polar molecules ( they are a special case of dipole-dipole forces ), while London forces occur between non-polar molecules.
Kagiso
how come the resultant force is 0
Andrew Reply
It's when you have equivalent forces going different directions then your resultant will be equal to zero
Temosho
describe what john's experiment proves about water molecules?
Fanozi Reply

Get the best Siyavula textbooks: gr... course in your pocket!





Source:  OpenStax, Siyavula textbooks: grade 11 physical science. OpenStax CNX. Jul 29, 2011 Download for free at http://cnx.org/content/col11241/1.2
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Siyavula textbooks: grade 11 physical science' conversation and receive update notifications?

Ask