Human Eye and Colourful World Test

Result

Human Eye and Colourful World Test - 28

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Weekly Quiz Competition

Question 1
1 / -0

A student sitting on the last bench can read the letters written on the blackboard but is not able to read the letters written in his textbook. Which of the following statements is correct?

A
The near point of his eyes has receded away.

B
The near point of his eyes has come closer to him.

C
The far point of his eyes has come closer to him.

D
The far point of his eyes has receded away.

Solution

A person suffering from hypermetropia is unable to see nearby objects distinctly. But the far away object are clear as the near point moves away beyond 25 cm.
Question 2
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Fine beam of light entering through a small hole in a dark room illuminates the particles in its path. Identify the effect associated with this process.

A
Schottky effect

B
Rutherford effect

C
Tyndall effect

D
Photoelectric effect

Solution

When fine beam of light entering through a small hole in a dark room, it illuminates the particle in its paths because of collision of particles of air and dust. This happens because of the Tyndall effect.
Question 3
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A prism ABC (with BC as base) is placed in different orientations. A narrow beam of white light is incident on the prism. In which of the following cases, after dispersion, the third colour from the top corresponds to the colour of the sky?

A
(i)

B
(ii)

C
(iii)

D
(iv)

Solution

The correction option here is B.
When the prism is placed with angle A in the upward direction, the third colour from top is yellow(refer image A). But we have been given the third color from top is that is blue( colour of the sky).
Thus, base BC must be on the top that is the prism must be inverted.
Question 4
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The clear sky appears blue because:

A
blue light gets absorbed in the atmosphere.

B
ultraviolet radiations are absorbed in the atmosphere.

C
violet and blue lights get scattered more than lights of all other colours by the atmosphere.

D
light of all other colours is scattered more than the violet and blue colour lights by the atmosphere.

Solution

The scattering of light depends on the size of the dust particles and the wavelength of the light. The amount of scattering is inversely proportional to the fourth power of wavelength.
Since, violet and blue lights get scattered more than lights of all other colours by the atmosphere the sky appears blue.
Question 5
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Which of the following statements is correct regarding the propagation of light of different colors of white light in air?

A
Red light moves fastest

B
Blue light moves faster than green light

C
All the colours of the white light move with the same speed

D
Yellow light moves with the mean speed as that of the red and the violet light

Solution

Air is not a dispersive medium and hence the light of all wavelengths travel with equal velocity.
Question 6
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The danger signals installed at the top of tall buildings are red in colour. These can be easily seen from a distance because among all other colours, the red light:

A
is scattered the most by smoke or fog.

B
is scattered the least by smoke or fog.

C
is absorbed the most by smoke or fog.

D
moves fastest in air.

Solution

The amount of scattering is inversely proportional to the fourth power of wavelength. And since the wavelength of red has the longest wavelength, the amount of scattering becomes smaller.
Danger signals installed at the top of tall buildings or traffic signals are red so that they can be easily seen from a distance.
Question 7
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A person needs a lens of power -4.5 D for correction of her vision. What kind of defect in vision is she suffering from?

A
Myopia

B
Ptosis

C
Presbyopia

D
Diplopia.

Solution

Negative sign of power of lens indicates that focal length of the lens used for correction is negative. This means that concave lens is used for correction. Concave lens is used for the correction of myopia and hence, the person is suffering from myopia.
Question 8
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Why is the colour of the clear sky blue?

A
Blue colour gets scattered the maximum.

B
water of sea is blue.

C
Blue colour gets scattered the minimum.

D
none of these.

Solution

Hint: Use the concept of scattering

Explanation:
Gases and particles in Earth's atmosphere scatter sunlight in all directions. Blue light is scattered more than other colours because it travels as shorter, smaller waves. And due to this we see the sky as blue.
Question 9
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How will you use two identical prisms so that a narrow beam of white light incident on one prism emerges out of the second prism as white light?

A
Just put them side by side.

B
one placed on top of the other .

C
one placed inverted with respect to the other.

D
none of these.

Solution

When two identical prisms are placed in such a way that one is placed inverted with respect to the other and a narrow beam of white light is incident on one, it emerges out of the second prism as white light. Angle of deflections of the two prisms are equal and opposite. While the first prism splits the light in the seven colours due to different angles of deflection, the second prism combines the spectrum along a single ray and the colours again combine to give white light as the emergent light.
Question 10
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When do we consider a person to be myopic?

A
He has poor near vision or blurred vision at all distances

B
He can not identify colors

C
He has poor night vision

D
He can see fine upto close distance, but distant objects are a blur

Solution

Myopia is the most common refractive error of the eye. It occurs when the eyeball is too long relative to the focusing power of the cornea and lens of the eye. This causes light rays to focus at a point in front of the retina, rather than directly on its surface. Such a person can see nearby objects clearly. However, far objects appear blurred to him.