Q: The power of a lens is defined as the reciprocal of its focal length. If the focal length is 0.5 m, what is the power in diopters?

$$P = \frac{1}{0.5} = 2\ \text{diopters}$$

Q: For a myopic eye with a far point of 50 cm, what lens is needed to focus sharply on an object at infinity?

A diverging lens with $$f = -50\ \text{cm}$$

Q: The angular magnification of the eyepiece in a microscope is:

$$M_2$$ = \frac{25\ \text{cm}}{$$f_2$$}$$

Q: A half-micron bacterium ($$0.5\ \mu\text{m}) is $$viewed under a microscope with a total magnification of $$2000\times. $$How large does the bacterium appear?

$$0.5\ \mu\text{m} \times 2000 = 1000\ \mu\text{m} = 1\ \text{mm}$$

Question 1

Which optical instrument is commonly used in medicine to examine the interior of the human body?

Accepted Answer

Endoscope

Question 2

What is the primary function of the cornea and lens in the human eye?

Accepted Answer

To produce a real image of the object being viewed

Question 3

A hyperopic (farsighted) eye forms the image of a nearby object:

Accepted Answer

Behind the retina

Question 4

Which type of lens is used to correct myopia (nearsightedness)?

Accepted Answer

Diverging lens

Question 5

The power of a lens is defined as the reciprocal of its focal length. If the focal length is 0.5 m, what is the power in diopters?

Accepted Answer

$$P = \frac{1}{0.5} = 2\ 	ext{diopters}$$

Question 6

A person with a hyperopic eye has a near point 100 cm in front of the eye. What focal length lens should be used to see clearly an object at 25 cm in front of the eye?

Accepted Answer

$$\frac{1}{f} = \frac{1}{s} + \frac{1}{s'} = \frac{1}{25} + \frac{1}{-100} = \frac{4}{100} - \frac{1}{100} = \frac{3}{100}$$, so $$f = 33.3\ 	ext{cm}$$

Question 7

For a myopic eye with a far point of 50 cm, what lens is needed to focus sharply on an object at infinity?

Accepted Answer

A diverging lens with $$f = -50\ 	ext{cm}$$

Question 8

The lateral magnification of the objective lens in a microscope is given by:

Accepted Answer

$$m_1$$ = -\frac{$$s_1$$'}{$$s_1$$}$$

Question 9

The angular magnification of the eyepiece in a microscope is:

Accepted Answer

$$M_2$$ = \frac{25\ 	ext{cm}}{$$f_2$$}$$

Question 10

The overall magnification of a compound microscope is:

Accepted Answer

$$M = m_1$ M_2$

Question 11

If a compound microscope has an objective lens with magnification $$m_1 = 40$ and an eyepiece with angular magnification M_2$ = 15$$, what is the total magnification?

Accepted Answer

$$M = 40 	imes 15 = 600$$

Question 12

A half-micron bacterium ($$0.5\ \mu	ext{m}) is $$viewed under a microscope with a total magnification of $$2000	imes. $$How large does the bacterium appear?

Accepted Answer

$$0.5\ \mu	ext{m} 	imes 2000 = 1000\ \mu	ext{m} = 1\ 	ext{mm}$$

Question 13

Which of the following best describes the image formed by the objective lens in a compound microscope?

Accepted Answer

A real, enlarged, and inverted image

Question 14

In the human eye, what happens when the ciliary muscle contracts?

Accepted Answer

The lens becomes more convex, decreasing its focal length to allow near vision

Question 15

A camera is an example of which type of optical instrument?

Accepted Answer

An optical instrument that uses lenses to form real images

Question 16

If the focal length of an eyepiece is $$5\ 	ext{cm}$$, what is its angular magnification?

Accepted Answer

$$M_2$$ = \frac{25\ 	ext{cm}}{5\ 	ext{cm}} = 5$$

Question 17

Which statement about the far point and near point of the eye is correct?

Accepted Answer

The far point is the maximum distance at which the eye can see clearly, and the near point is the minimum distance

Question 18

Which optical instrument is used to examine the retina during an eye examination?

Accepted Answer

Ophthalmoscope

Question 19

A person with a myopic eye can see objects clearly only up to 50 cm. What is the power of the lens required to correct their vision for distant objects?

Accepted Answer

$$P = \frac{1}{f} = \frac{1}{-0.5} = -2\ 	ext{diopters}$$

Optical Instruments: The Eye, Vision Correction, and the Microscope

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