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Physics > Human Eye And Colorful World > Flashcards

Human Eye And Colorful World Flashcards

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1
Q

Diameter of eyeball

A

2.3 cm

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2
Q

Cornea

A

Outermost transparent bulge, thin membrane

Most refraction occurs at its surface

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3
Q

Crystalline lens

A

Fibrous Jelly like material, convex lens

Provids finer adjustment of focal length

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4
Q

Iris

A

Dark muscular diaphragm

Controls side of the pupil

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5
Q

Pupil

A

Central aperture in the iris

Regulates the amount of light entering the eye

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6
Q

Retina

A

Delicate membrane with light sensitive cells

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7
Q

Briefly explain how we are able to see things

A

Light reaches retina
Light sensitive cells get activated upon illumination and generate electrical signals
Signals reach brain via optic nerves
Brain processes signals and we see

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8
Q

Ciliary muscle function

A

Change the curvature of eye lens and hence its focal length

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9
Q

Accommodation of eye, definition

A

The ability of the eye lens to adjust its focal length

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10
Q

When object is close, do ciliary muscles contract or relax?

A

Contract, decrease focal length

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11
Q

Define near point

A

The minimum distance at which we can see objects clearly withour strain

About 25 cm

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12
Q

Define far point

A

Farthest distance we can see objects clearly

Infinity

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13
Q

What is a cataract

A

When crystalline lens becomes milky and cloudy often at old age

Causes partial or complete loss of vision

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14
Q

Why do we have two eyes

A

Wider field of view: 150 vs 180 degrees

Stereopsis: depth, combines two images to understand how far things are

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15
Q

Myopia
Definition + cause + correction

A

Near sightedness
Cannot see distant objects clearly
Aka far point nearer than infinity

Image is formed in front of retina

Excessive curvature of eye lens
Elongation of eyeball

Concave lens

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16
Q

Hypermetropia
Definition + cause + correction

A

Far sightedness
Cannot see nearby objects clearly
Near point is farther than 25 cm

Image formed behind retina

Focal length is too long
Eyeball becomes small

Convex lens

17
Q

Presbyopia

A

Similar to hypermetropia except cause is old age
Near point gradually recedes with time due to gradual weakening of ciliary muscles and flexibility of eye lens

18
Q

Bi focal lens

A

For people with both myopia and hypermetropia
Upper portion concave
Lower portion convex

19
Q

What is a prism

A

Two triangular bases and three rectangular lateral surfaces

20
Q

Dispersion, who was the first to obtain it with a prism

A

The spitting of white light into into its component colours

Isaac newton

21
Q

How are rainbows formed

A

Dispersion of sunlight by water droplets

Refract and disperse > reflect it internally > refract it again when it comes out

Always formed in direction opposite to the sun

22
Q

Explain the flickering/wavering above fire

A

Hotter air is less dense (and hence has a lesser refractive index) than cooler air above.

Hot air rises and cool air also moves, so the refractive index fluctuates

23
Q

Why do stars twinkle? Why not planets?

A

Star light refracts continuously in the atmosphere. The refractive index gradually changes.
Hence atmospheric refraction bends starlight towards normal and its apparent position appears slightly lower.

Atmosphere is not stationary so the path of light always varies slightly, and the amount of starlight entering the eye varies: brighter/fainter. Twinkling effect.

Planets are much larger, variation in amount of light entering our eyes is negligible

24
Q

How does atmospheric refraction effect sunrise senset

A

Sunrise 2 minutes early
Sunset 2 minutes late

Sun appears higher than actual position, like stars

25
Q

Tyndall effect
What is scattering of light

A

Spreading of light in various directions by colloid particles (when light deviates from its straight path)

When light passes through a colloid, its path becomes visible

Ex, dust, dense canopy water droplets in misy

26
Q

Why is the sky blue

A

Molecules of air etc are smaller than the wavelength of visible light
These are more effective in scattering light of shorter wavelength (blues) than longer wavelength (red)

27
Q

If earth had no atmosphere

A

No scattering of light would take place, dark

Example passengers at high altitudes see a dark sky as atmosphere is thinner and scattering is less prominent

28
Q

Why are danger signals red

A

Red is least scattered by fog smoke etc, it can be seen as red from a distance

29
Q

Why are clouds white

A

Water/ice/dust droplets are large, all colors of light are scattered, they appear white

30
Q

Why does sunrise/sunset appear red

A

Sun is near the horizon hence it travels a larger distance in the atmosphereand thick layers of atmosphere

Short wavelength (blues) is scattered away and long wavelength (reds) reaches our eyes

31
Q

At noon, the sky is almost white

A

Sunlight travels least distance, only a little bit of blues (short wavelength) is scattered

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