G10 Optical Instruments Flashcards
is a hand-held tool used to view smaller objects
one of the simplest optical instruments and is comprised of just a single converging lens
magnifying glass
As the object moves _ to the eye, the angle increases and as a result, a _ image is observed.
closer, larger
However, the eye cannot focus on an object closer than 25 cm. This is referred to as the
near point
However, the eye cannot focus on an object closer than 25 cm. This is referred to as the
near point
To increase the apparent size of the object being observed, a _ _ can be placed in front of the eye while the object is positioned at the focal length of the lens.
converging lens
In this setup, the virtual image is at _, making the muscle of the eye more relaxed and the image more comfortable to view.
infinity
The image formed by the magnifying glass is always _, _, and _
virtual, upright in position, and enlarged.
angular magnification
efficiency of a magnifier
given by the ratio of the angle with the magnifier (θ) to the angle without the magnifier (θ0)
If the object is at the near point of the eye, the maximum angular magnification is given by this equation
m(max)=1+25cm/f
regular angular magnification
m=θ/θ(0)
angle with the magnifier (θ) to the angle without the magnifier (θ0).
The object must be placed at the focal point of the lens for the image to be at infinity. This relationship is expressed by the equation
m=θ/θ0=25cm/f
angle with a magnifier
θ
angle without a magnifier
θ0
focal length
f
Higher magnification that cannot be provided by a simple magnifier can be achieved by using a combination of two lenses in a device
microscope, sometimes compound microscope
used to focus the object under the microscope with wide range of magnifications and a very short focal length which is usually less than one centimeter
objective lens
used to observe the object or specimen being studied. It usually has a magnification of 10 to 15 times and a focal length of a few centimeters
ocular lens
ocular lens is also called
eyepiece
The image formed by the _ lens, becomes the object for the _ lens.
objective, ocular
The object is placed outside the focal length of the objective which forms a _, _ and _ image that is at or inside the focus of the eyepiece
real, inverted and enlarged
The eyepiece which acts as a simple magnifier uses the image produced by the objective lens as its ‘_’.
object
The eyepiece which acts as a simple magnifier uses the image produced by the objective lens as its ‘object’. As a result, it produces a second image which is considered as the “_”.
final image
This second image that we observe is _, _, and _ compared to the original object.
virtual, inverted and very much enlarged
The angular magnification between the angular sizes of the virtual image as seen through the eyepiece and of the real image if viewed without the eyepiece is expressed by the equation below:
m=M(1)m(e)=[-L/f(o)][25cm/f(e)]
overall magnification of the compound microscope
m
lateral magnification of the objective lens
M(1)
angular magnification of the eyepiece
m(e)
distance between the objective lens and eyepiece
L
focal length of the objective lens
f(o)
focal length of the eyepiece
f(e)
optical system that is used to view distant objects. This is used to view large objects at huge distances while microscopes are used to view small objects close at hand
telescope
uses a combination of two lenses to form an image
refracting telescope
The objective lens forms a _ and _ image of a distant object either near or exactly at the focal point of the eyepiece.
real and inverted
The second image or the final image seen in the eyepiece is an _, _ and _ image of the actual object.
enlarged, virtual, and inverted
are useful in viewing relatively nearer objects, such as the sun, the moon or the planets
Refracting telescopes
Very distant objects, such as stars will always appear as _ _ _ _no matter how angular magnification is increased
miniscule points of light
angular magnification of a refracting telescope is given by
m=θ/θ(o)=f(o)/f(e)
angle subtended by the object at the objective lens
θ(o)
angle subtended by the final image at the eyepiece lens
θ
focal length of the objective lens
f(o)
focal length of the eyepiece lens
f(e)
uses a combination of a curved mirror and a lens to form an image
type of telescope is commonly used when viewing very far objects such as stars
reflecting telescope
simply a pair of small telescopes attached side by side. It is used to view images of greater depth
Binoculars
image formed using binoculars
upright
an optical device used for recording images either electronically or on film
camera
working principle is similar in many ways on the structure and function of the _ _
(camera)
human eye
has a _ which works similarly to the eyelid of the human eye.
allows the light to enter when opened and blocks the light when closed
shutter
The hole behind the camera is called _, similar to the eye’s pupil.
It serves as the pathway of light to the camera
aperture
Another part of a camera is the _. It functions similarly to the iris.
It regulates the amount of light entering the aperture which affects the lighting in a photograph.
diaphragm
camera has used this to focus the light to produce bright and clear images
converging lens
Lastly, a camera has a converging lens used to focus the light to produce bright and clear images. The lens forms an _, _ image on the recording medium.
inverted, real
The recording medium is similar to the eye’s
retina.
Diaphragm functions similarly to the _.
iris
Aperture is similar to the eye’s _
pupil
shutter which works similarly to the _
eyelid
When a camera is in focus, the position of the recording medium is at the _ position as that of the image formed by the lens.
same
When a camera is in focus, the position of the recording medium is at the same position as that of the image formed by the lens.
This results in a _ image.
sharp
Remember that in a converging lens, the image distance _ as the object distance _.
increases, decreases
Generally speaking, capturing an image of a distant object requires a lens of longer focal length. This is commonly called as _.
zoom lens
A lens of shorter focal length produces a smaller image but larger field of view. This is commonly known as “_ _ lenses” or ‘_’ lenses.
wide angle, fisheye
The amount of light entering the lens is controlled by the _ _ and its _ _.
camera’s shutter and lens aperture
The _ regulates the time interval by which light is allowed to enter the lens
shutter
This factor can be adjusted in a camera to factors of about 2, usually from _ to _.
1s to 1/1000 s
Photographers refer to this light-gathering capability as the f-number of the lens which is mathematically expressed as
f-number=f/d
focal length
f
D
aperture diameter
The _ _ _ increases with the f-number
depth of field
forms an image with objects at one distance in focus and the rest of the image out of focus
low f-number
forms a sharp image of an object at very far distances
high f-number
