Human Eye and Colourful World Test

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Human Eye and Colourful World Test - 38

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Weekly Quiz Competition

Question 1
1 / -0

At sun rise or at sun set the sun appears to be reddish while at mid day it looks white. This is because

A
Scattering due to dust particles and air molecules causes this phenomenon

B
The sun is cooler at sun rise or at sunset

C
Refraction causes this phenomenon

D
Diffraction sends red rays to the earth at these times

Solution

It is due to scattering of light. At noon, the sun is at the nearest point to earth. Hence all the colors get scattered almost equally and this you see white light.
But during sunrise and sunset, the sun is at the longest position. Here blue light gets scattered off and due to larger wavelength of the red light it can travel a longer distance and hence reach our eyes. This we see the sun red.

Option A is correct.
Question 2
1 / -0

A person cannot see objects clearly which are nearer than 75 cms from his eyes, the disease he is suffering from is:

A
Astigmatism

B
Myopia

C
Hypermetopia

D
Presbyopia
Question 3
1 / -0

A person can see clearly up to 3 metres what should be the power of the lens in his spectacles so that he could see clearly up to 12 metres.

A
0.25 D

B
-0.25 D

C
0.5 D

D
- 0.75 D

Solution

Answer is B.

The lens equation is given as $$\displaystyle \frac{1}{u}+ \frac{1}{v} = \frac{1}{f}$$
$$\displaystyle \frac{1}{1200} + \frac{1}{-300} - \frac{1}{f}$$ (u and v are in cm)

The negative sign is due negative value of the image distance of the concave lens.
$$f = - 400\ cm$$
Power $$=\displaystyle \frac{100}{f}$$ in cm.
So, $$\displaystyle \frac{100}{-400} = - 0.25 D$$.
Hence, the power of the lens in his spectacles is -0.25D.
Question 4
1 / -0

Reflection of the sunlight from the upper layers of the Earth's atmosphere causes

A
days and nights

B
tides

C
eclipses

D
twilight

Solution

You can define twilight simply as the time of day between daylight and darkness, whether that’s after sunset, or before sunrise. It’s a time when the light from the sky appears diffused and often pinkish. The sun is below the horizon, but its rays are scattered by Earth’s atmosphere to create the colors of twilight.

We have twilight because Earth has an atmosphere. Some light scatters through small particles in the atmosphere – so there’s still some light in the sky even after the sun has gone down.
Question 5
1 / -0

Figure (a), (b), and (c) respectively, indicate the point of focus in case of :

A
The normal eye, the hypermetropic eye and myopic eye

B
The hypermetropic eye, the mypoic eye and the normal eye

C
The normal eye, the myopic eye and the hypermetropic eye

D
The myopic eye, the normal eye and the hypermetropic eye

Solution

Normal eye forms an image at retina. A myopic eye forms an image before retina whereas a hypermetropic eye forms image behind retina.
Question 6
1 / -0

Long-sightedness is caused by the eyeball being too short. It can be corrected by the use of a :

A
convergent lens

B
plane mirror

C
divergent lens

D
concave mirror

Solution

In long sightedness, size of the eyes ball decrease due to which image of the object formed behind the ratina. This defect can be corrected by using additional converging lens of sufficient power. That lens will help the eyes to formed image on the ratina. Hence converging lens required.
Question 7
1 / -0

Hypermetropia is due to the ________ of the eye.

A
low converging power

B
low diverging power

C
high converging power

D
high diverging power

Solution

Hypermetropia, sometimes called hyperopia, is the term used to define being longsighted. In hypermetropia, the image of a nearby object form behind the retina. This means that light is focused too far back in the eye. This happen due to decrement in converging power of eyes lens.
Hence, Hypermetropia is due to the low converging power of the eye.
Question 8
1 / -0

A person cannot see the objects clearly placed at distance more than $$40\ cm$$. He is advised to use lens of power:

A
$$-2.5\ D$$

B
$$+2.5\ D$$

C
$$-6.25\ D$$

D
$$+1.5\ D$$

Solution

That lens should be given to the person which forms the image of an object at infinity at distance 40 cm in front of the eye.

Hence, $$u=-\infty$$ and $$v=-40cm$$

Now,

$$\dfrac{1}{f}=\dfrac{1}{v}-\dfrac{1}{u}$$

$$\implies \dfrac{1}{f}=\dfrac{-1}{40}-\dfrac{1}{-\infty}$$

$$\implies f=-40cm$$

$$P=\dfrac{100}{f(cm)}=\dfrac{-100}{40}=$$

$$\implies P=-2.5D$$

Answer-(A).
Question 9
1 / -0

A near sighted person cannot see distinctly beyond $$50 cm$$ from his eye. The power in diopter of spectacle lenses which will enable him to see distant objects clearly is:

A
+50 D

B
-50 D

C
+2 D

D
-2 D

Solution

When a person cannot see far situated object we assume object distance to infinity.

Then image distance be v = -50cm

$$u=\infty \\ v=-50cm$$

then,

$$\dfrac { 1 }{ f } =\dfrac { 1 }{ v } -\dfrac { 1 }{ u } \\ \dfrac { 1 }{ f } =-\dfrac { 1 }{ 50 } \\ f=-50cm=-0.5m$$ (concave lens)

$$power=\dfrac { 1 }{ f } =\dfrac { 1 }{ 0.5 } =-2D$$
Question 10
1 / -0

Figures (a), (b), (c) and (d) respectively correspond to

A
The short-sighted eye, the correction of long-sight, the long-sighted eye and the correction of short-sight

B
The short-sighted eye, the correction of short-sight, the long-sighted eye and the correction of long-sight

C
The long-sighted eye, correction of short-sight, the short-sighted eye and the correction of long-sight

D
The long-sighted eye, the correction of long-sight, the long-sighted eye and the correction of short-sight

Solution

In Myopia eyes, Images of an object form before the retina so for correction diverging lens are used.
In Hypermetropia eyes, Images of an object formed behind the retina so for correction converging lens are used.
Hence,
R.E.F image
(a) Myopia of short-sightedness
R.E.F image
(b) Corrected short-sightedness
R.E.F image
(c) Hypermetropia or long-sightedness
R.E.F image
(d) Corrected hypermetropia

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Re-Attempt Weekly Quiz Competition

Human Eye and Colourful World Test - 38

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Human Eye and Colourful World Test - 38

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SHARING IS CARING

Question 1

Scattering due to dust particles and air molecules causes this phenomenon

The sun is cooler at sun rise or at sunset

Refraction causes this phenomenon

Diffraction sends red rays to the earth at these times

Solution

Question 2

Astigmatism

Myopia

Hypermetopia

Presbyopia

Question 3

0.25 D

-0.25 D

0.5 D

- 0.75 D

Solution

Question 4

days and nights

tides

eclipses

twilight

Solution

Question 5

The normal eye, the hypermetropic eye and myopic eye

The hypermetropic eye, the mypoic eye and the normal eye

The normal eye, the myopic eye and the hypermetropic eye

The myopic eye, the normal eye and the hypermetropic eye

Solution

Question 6

convergent lens

plane mirror

divergent lens

concave mirror

Solution

Question 7

low converging power

low diverging power

high converging power

high diverging power

Solution

Question 8

$$-2.5\ D$$

$$+2.5\ D$$

$$-6.25\ D$$

$$+1.5\ D$$

Solution

Question 9

+50 D

-50 D

+2 D

-2 D

Solution

Question 10

The short-sighted eye, the correction of long-sight, the long-sighted eye and the correction of short-sight

The short-sighted eye, the correction of short-sight, the long-sighted eye and the correction of long-sight

The long-sighted eye, correction of short-sight, the short-sighted eye and the correction of long-sight

The long-sighted eye, the correction of long-sight, the long-sighted eye and the correction of short-sight

Solution

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