The Nature of Convex Lens
1. Objects are located between O and F
A′B ′ = virtual shadow in front of the lens
F1 = focus behind the lens
F2 = focus in front of the lens Shadow image: virtual, upright, enlarged
2. Objects are located between F2 and 2F2
The A′B shadow is: real, inverted, enlarged3.
3. Items between F2 to ~
Shadow A′B bersifat, is: real, inverted, reduced.
From the three paintings:
If the object is located between O and F, the nature of the virtual image, upright, in the area.
If the object is located between F and 2F the nature of the image is real, inverted, enlarged.
If s = f the image is erect, virtual, at infinity
If s = 2 f, the shadow is reversed, real, equal
If s> 2f, the real image, inverted, is reduced
Shadow enlarged | s ′ | > s, the shadow is reduced if | s ′ | <s. (Note: | –5 | = 5 or | 5 | = 5)
4. Objects located in focus at (F)
Objects are in focus at (F) Objects in focus (s = f), easily observable shadows are: virtual, upright, enlarged.
5. Objects are located at 2 F (s = 2f)
Objects located at 2 F (s = 2f) Real, inverted, equal shadows
Objects in 2F2, shadows 2F1 are: real, inverted, equal.
From the five paintings it can be concluded:
All virtual shadows formed by convex lenses are always upright against the object.
All real images formed by convex lenses must be inverted to the object.
Relationship between s, s ′ and f Convex Lens
Observation or practicum uses convex lenses, candles.
Observation using a convex lens with:
f = 20 cm.
s = object distance
s ′ = shadow distance
By moving the screen away from or approaching the screen if s> 20, you will get a sharp shadow on the screen. Usually observations or practicums such as the state of distance between objects and shadow distance are written into the table. Then the shadow distance and object distance are changed and measured when the shadow on the screen is clear enough.
The results are as in the table below
Convex Lens Formula
Formula for finding convex lens focus:
Information:
nu is the refractive index of air or water
R1 and R2 are the curvature of the convex lens
The formula for finding the shadow distance on a convex lens:
1 / f = 1 / s + 1 / s ’
Information:
f = convex lens focus
s = object distance
s ’= shadow distance
The nature of the image formed by the convex lens is real, inverted and enlarged.
Zoom in convex lens (M)
M = S '/ S or M = h' / h or can be with the formula M = f / (s-f)
Benefits and Uses of Convex Lenses in Daily Life
For people who cannot read within a normal distance of 25 or people who suffer from nearsightedness (myopia) can be helped with convex-lensed glasses to be able to read within 25 cm or see normally.
To observe celestial bodies to make them look clearer and closer to astronomers, use binoculars two convex lenses
Biologists or laboratory workers observe bacteria, etc. using a microscope that uses a convex lens.
Convex lens used on magnifying magnifying glass. For example a clock servicer who uses a magnifying glass to observe a small clock component.
Convex lenses are also used on periscopes, slide projectors, episcopes, cinema projectors etc.