Lens power

Question 1

Find the focal lengths of the given lenses.

a. D = +2.00D f = ___mm
b. D = +10.00D f = ___mm
c. D = -0.50D f = ___cm
d. D = -2.50D f = ___mm

Answer 1

a. f = .5 M
b. f = 100mm
c. f = 200cm
d. f = 400mm

Question 2

Find the dioptric power of lenses having the following focal lengths.

a. f = +4.0 meters, D = ___
b. f = +20mm, D = ___
c. f = -333mm, D = ___
d. f = -25cm, D = ___

Answer 2

a. D = +0.25D
b. D = +50.00D
c. D = -3.00
d. D = -4.00

Question 3

What is the dioptric power of a lens with a focal length of each of the following?

a. 25mm = ___
b. 2.5mm = ___
c. 25cm = ___

Answer 3

a. 40.00D
b. 400.00D
c. 4.00D

Question 4

What is the focal length of a +5.00D lens in ___

a. Meters? = ___
b. Millimeters? = ___

Answer 4

a. .2

b. 200

Question 5

What is the focal length of a +0.50D lens in ___

a. Centimeters? = ___
b. Meters? = ___

Answer 5

a. 200

b. 2

Question 6

What dioptric power is required to focus at 40cm?

Answer 6

+2.50D

Question 7

What is the focal length of a +3.00D lens in centimeters?

Answer 7

33cm

Question 8

What is the power of a lens if it brings incident light to a focus 20mm away?

Answer 8

+50.00D

Question 9

What is the focal length of a -0.50D lens?

Answer 9

-2M

Question 10

What is the focal length of a -2.50D lens in centimeters?

Answer 10

-40cm

Question 11

What is the power of a lens with a virtual focus 40mm away?

Answer 11

-25.00D

Question 12

What is the power of a lens with real focus 4M away?

Answer 12

+0.25D

Question 13

What is the focal length of a +10.00D lens in cm?

Answer 13

10cm

Question 14

What is the focal length of a +1.00D lens in meters?

Answer 14

1M

Question 15

A +2.50D lens will focus light ___ mm away.

Answer 15

400

Question 16

A lens focuses light 4M away. What is the power of the lens?

Answer 16

+0.25D

Question 17

A minus lens has a focal length of 25cm. What power is the lens?

Answer 17

-4.00D

Question 18

A lens with a focal length of 80cm is a ___

Answer 18

+1.25D lens

Question 19

Find the nominal power

Answer 19

1

Question 20

Find the back surface

Answer 20

2

Question 21

Find the front surface

Answer 21

3

Question 22

4

Answer 22

-4.50D

Question 23

5

Answer 23

+7.00D

Question 24

6

Answer 24

-11.00D

Question 25

Sagittal depth is the straight-line distance between the back surface of a lens at its vault and the chord diameter of the lens. true or false

Answer 25

true

Question 26

If the radius of a surface remains the same and the diameter changes, the thickness will change but the sagittal depth will remain the same. true or false

Answer 26

false

Question 27

If the radius of a surface is reduced and the diameter remains the same, the thickness will be reduced. true or false

Answer 27

true

Question 28

If the sagittal depth remains the same, and the diameter increases, the surface will become flatter. true or false

Answer 28

true

Question 29

If the sagittal depth remains the same, and the diameter increases, the surface will become flatter. true or false

Answer 29

true