13) Optical Lenses

Question 1

Optical lens

Answer 1

Optically homogeneous grandparent body

Question 2

Types of thickness

Answer 2

Thin lenses
The thickness is smaller than the curvature

Tick
The thickness is neglible relative to curvature

Question 3

Types of lenses by the shape of their surface

Answer 3

Spherical
They have 2 spherical ends

Cylindrical
Bound by 2 cylindrical ends

Question 4

Type of lenses by the curvature

Answer 4

Biconvex
The shape looks like ()

Biconcave
Looks like rectangle with bite missing

Question 5

Type of lenses by the refraction

Answer 5

You have converging
This is when it increases the convergence of the incidence and decreases the diverging

Diverging is vice Versa

Question 6

Basic elements of the spherical lens

Answer 6

Principle optical axis _
Principle plane l
Optical centre 
Focus 
Focal plane l 
Focal length

Question 7

Optical power

Answer 7

This depends on the curvature

Positive is converging
Negative is diverging

Question 8

Thin lens formula

Answer 8

1/F= 1/A 1/B

a is the object distance
b is the image distance
F is the focal length

Question 9

Refraction of cylindrical lens

Answer 9

The cross section is rectangular this means that the rays are not refracted

Question 10

Aberrations

Answer 10

This is the distortion of an image

Question 11

Spherical aberrations

Answer 11

The rays further away from the axis are refracted more

The image of the point is blurry

Use compound lens

Question 12

Chromatic aberration

Answer 12

The focal length different for rays of different colour

Point image is coloured

Use compound lens

Question 13

Distortion

Answer 13

This is when the magnification is altered

Causes barrel

Use a compound lens

Question 14

Field curvature

Answer 14

This is when the planar object is not image onto the plane

Image can’t be seen

Compound lens

Question 15

Astigmatism

Answer 15

The point will appear as a eclipse or circle

Correction is using compound lens but it can’t be totally eliminated

Question 16

Coma

Answer 16

This means the image appears as a off centre spot

Correction is use of a compound lens

Question 17

Optical system of the eye coats the globe

Answer 17

The cornea
This is a transparent layer found before the iris and pupil

Iris
Coloured cells found before the lens

Pupil
A circular opening that can change its diameter to act as an apature

Question 18

Optical system of the eye anterior and posterior

Answer 18

This is present behind the cornea but before the lens

Question 19

Eye lens

Answer 19

This consists of a double convex transparent layer behind the pupil

The front and back have different curvatures

Question 20

Optical system of the eye

Answer 20

The retina

Is the inner layer of sensitive light cells

Question 21

Control of the radiant flux surface

Answer 21

The eyelid stood light beam from entering the eye

The pupil can change its diameter to let more or less light in

Question 22

Optical system of the eye

Answer 22

The optical power of the eye varies

It’s around 60D when it focuses on objects that are further away

Around 74D when it focuses on objects closer to the eye

Question 23

Image on the retina

Answer 23

This image is
Inverted
read
Diminished

Question 24

Accommodation

Answer 24

This is the optical power needed to focus on an object that is much closer to the eye

This distance increases with age

Question 25

Normal near point distance

Answer 25

This is the closest an object can be to the face for the eyes to sill focus and for it to still be comfortable