Human Eye and Colourful World Test

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Human Eye and Colourful World Test - 47

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Weekly Quiz Competition

Question 1
1 / -0

Scattering of light is seen when light passes through:

A
During formation of rainbow

B
Reflected by a mirror

C
passed through a prism

D
Canopy of dense forest

Solution

When the sunlight enters the dense forest, the rays of light pass through these particles of colloids and get scattered. Hence Scattering occurs when light passes through canopy of dense forests.
Question 2
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Due to refraction, sunrise appears ______ sun comes to horizon and sunset appears______sun leaves horizon respectively.

A
before, after

B
after, before

C
before, before

D
after, after

Solution

Due to refraction, light bends and sunrise appears before sun comes to horizon whereas sun disappears after leaving the horizon.
Question 3
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What causes difference in velocity of colours while passing from one medium to another through glass prism?

A
Different wavelengths

B
Different amplitudes

C
Different colours

D
None of the above

Solution

Different wavelengths causes difference in velocity of colours while passing from one medium to another through glass prism,because every colour has different wavelength.And refractive index depends on wavelength of light so different wavelength mean different refractive index which means different velocities.
Question 4
1 / -0

When white light passed through glass prism, why dispersion occurs?

A
Colours of white light travels at different speeds through prism

B
Colours of white light travels at same speeds through prism

C
Colours of white light travels at different acceleration through prism

D
Colours of white light travels at same acceleration through prism

Solution

$$Answer:-$$ A
A light ray is refracted (bent) when it passes from one medium to another at an angle and its speed changes. At the interface, it is bent in one direction if the material it enters is denser (when light slows down) and in the other direction if the material is less dense (when light speeds up). Because different wavelengths (colors) of light travel through a medium at different speeds, the amount of bending is different for different wavelengths. Violet is bent the most and red the least because violet light has a shorter wavelength, and short wavelengths travel more slowly through a medium than longer ones do. Because white light is made up of all visible wavelengths, its colors can be separated (dispersed) by this difference in behavior.
Question 5
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When the white light passes through prism, it splits into..............colours.

A
5

B
8

C
7

D
9

Solution

When white light passes through some transparent material such as glass prism, it splits into its seven constituent colors i.e. violet, indigo, blue, green, yellow, orange, and red (VIBGYOR) This phenomenon of splitting of white light is known as dispersion of light.
Question 6
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Intensity of light ray in a direction after scattering by small particles (smaller than wavelength):

A
decreases.

B
remains the same.

C
increases.

D
may increase or decrease depending on the medium in the corresponding direction.

Solution

After scattering of light by small particles, it spreads in all directions. Hence, the intensity of the scattered light in a direction is smaller then the intensity of the incident light wave.
Question 7
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After scattering, the light moves in:

A
the same direction as the original light ray.

B
opposite to the original direction of the light ray.

C
all directions.

D
the direction of the shortest path.

Solution

In scattering, light is absorbed and re-emitted in all directions (as seen in the figure) without a change in the wavelength of the light ray.

A light of a given wavelength is scattered only by a particle of a size comparable to the wavelength. The colour of the scattered light depends on the size of the scattering particles. Very fine particles scatter mainly blue light while particles of larger size scatter light of longer wavelengths. If the size of the scattering particles is large enough, then, the scattered light may even appear white.
Question 8
1 / -0

Which of the following quantities change during the process of scattering?

A
Speed.

B
Wavelength.

C
Direction of propagation.

D
None of the above.

Solution

After scattering, light is spread in all directions and hence the direction of propagation changes. Wavelength, speed and frequency of the light remains unchanged during the process. Also, the intensity of the light ray in a direction changes.
Question 9
1 / -0

The least distance of vision of a long-sighted person is $$60 \ cm$$. By using a spectacle lens, this distance is reduced to $$12 \ cm$$. The power of the lens is:

A
$$+5.0 \ D$$

B
$$+\dfrac{20}{3} \ D$$

C
$$-\dfrac{10}{3} \ D$$

D
$$+2.0 \ D$$

Solution

Given that the least distance of vision is $$60 \ cm$$, which is reduced using a lens to $$12 \ cm$$. This implies that the image of an object at $$12 \ cm$$ is formed at $$60 \ cm$$ from the lens.

Hence, $$v=-60 \ cm$$ , $$u=-12 \ cm$$
$$\therefore$$ by using the lens' formula $$\cfrac { 1 }{ f } =\cfrac { 1 }{ v } -\cfrac { 1 }{ u } $$
We have $$\cfrac { 1 }{ f } =\cfrac { 1 }{ -60 } -\cfrac { 1 }{ -12 } $$
$$\Rightarrow \cfrac { 1 }{ f } =\cfrac { 1 }{ 15 }{cm}^{-1} $$ or $$\cfrac { 100 }{ 15 } m^{-1}$$
So, the power of lens, $$P=\dfrac{1}{f} = \cfrac { 100 }{ 15 } =+\cfrac { 20 }{ 3 } D$$
Question 10
1 / -0

When is the intensity of scattered light independent of the wavelength?

A
Medium of travel is not air.

B
Particles involved in scattering have size smaller than the wavelength of the incident light wave.

C
Particles involved in scattering have size larger than the wavelength of the incident light wave.

D
Particles scattering the light wave are not neutral in charge.

Solution

When the particles involved in scattering are of comparable or smaller size of the wavelength of light, then the intensity of scattered light is inversely proportional to the fourth power of the wavelength. This is known as the Rayleigh scattering. Hence, in visible spectrum, they scatter violet the most and red the least.

However, when the particles are larger than the wavelength of light, then the scattering of all wavelengths occur to same extent, i.e. the intensity of scattered light is independent of the wavelength.