11. The Human Eye and the Colourful World

SEBA Class 10 Science Chapter 11. The Human Eye and the Colourful World

Chapter 11. The Human Eye and the Colourful World

Class 10 Science Chapter 11 The Human Eye and the Colourful World Multiple Choice Questions and Answers :

Question : The human eye can focus objects at different distances by adjusting the focal length of the eye lens. This is due to

(a) presbyopia.

(b) accommodation.

(d) far-sightedness.

Answer : (b) accommodation.

Question : The human eye forms the image of an object at its

(a) cornea.

(b) iris.

(d) retina.

Answer : (d) retina.

Question : The least distance of distinct vision for a young adult with normal vision is about

(a) 25 m.

(b) 2.5 cm.

(d) 2.5 m.

Answer : (c) 25 cm .

Question : The change in focal length of an eye lens is caused by the action of the

(a) pupil.

(b) retina.

(d) iris.

Answer : (c) ciliary muscles.

Question : The formation of rainbow [SEBA 2021]

(a) Occurs in the same direction as the sun

(b) Occurs in the opposite direction as the sun

(d) None of the above

Answer : (b) Occurs in the opposite direction as the sun.

[ The formation of a rainbow is a result of the refraction, dispersion, and reflection of sunlight in water droplets in the atmosphere. ]

Question : Which of the following is responsible for change in the curvature of eye lenses ?

(a) Retina

(b) Iris

(d) Optic nerve

Answer : (c) Ciliary muscles .

[ The structure responsible for the change in the curvature of the eye lens is ciliary muscles.]

Question : A person cannot see distinctly objects kept beyond 2 m. This defect can be corrected by using a lens of power

(a) + 0.5 D

(b) – 0.5 D

(d) – 0.2 D

Answer : (b) – 0.5 D

[ Since the person cannot see distinctly objects beyond 2 meters, the person is experiencing myopia or nearsightedness. To correct myopia, a concave lens is needed.

Here, m

We have ,

So, the person can correct the defect by using a concave lens with a power of - 0.5 diopters.]

Question : 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 text book. 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

(d) The far point of his eyes has receded away

Answer : (a) The near point of his eyes has receded away.

[ When a person can see the letters on the blackboard (which is at a distance) but has difficulty reading the letters in the textbook (which is closer), it indicates that the near point of the eyes has receded. The near point is the closest distance at which an object can be brought into focus, and it tends to increase with age or certain eye conditions. ]

Question : A prism ABC (with BC as base) is placed in different orientations. A narrow beam of white light is incident on the prism as shown in Figure 11.1. 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)

Answer : (b) (ii)

Question : At noon the sun appears white as

(a) light is least scattered

(b) all the colours of the white light are scattered away

(d) red colour is scattered the most

Answer : (b) all the colours of the white light are scattered away.

[ When the sun is higher in the sky, the Earth's atmosphere scatters shorter wavelengths of light (blue and violet) more effectively than longer wavelengths. However, at noon, the sunlight has a shorter distance to travel through the atmosphere, and much of the shorter wavelengths get scattered, leaving the longer wavelengths (red, orange, yellow, and green) dominant. As a result, the direct sunlight appears white.]

Question : Which of the following phenomena of light are involved in the formation of a rainbow?

(a) Reflection, refraction and dispersion

(b) Refraction, dispersion and total internal reflection

(d) Dispersion, scattering and total internal reflection

Answer : (c) Refraction, dispersion, and internal reflection.

[ Rainbows are formed when sunlight is refracted, dispersed (split into its different colors), and internally reflected within raindrops in the atmosphere. This combination of phenomena leads to the separation of sunlight into its various colors and the creation of a circular arc of colors that we perceive as a rainbow. ]

Question : Twinkling of stars is due to atmospheric

(a) dispersion of light by water droplets

(b) refraction of light by different layers of varying refractive indices

(d) internal reflection of light by clouds

Answer : (b) refraction of light by different layers of varying refractive indices in the Earth's atmosphere.

[ As starlight passes through the Earth's atmosphere, it encounters air layers with varying temperatures and refractive indices. These variations cause the starlight to refract differently, leading to the twinkling effect that we observe. ]

Question : The clear sky appears blue because

(a) blue light gets absorbed in the atmosphere

(b) ultraviolet radiations are absorbed in the atmosphere

(d) light of all other colours is scattered more than the violet and blue colour lights by the atmosphere

Answer : (c) violet and blue lights get scattered more than lights of all other colors by the atmosphere.

[ During the day, when the sun is higher in the sky, the Earth's atmosphere scatters shorter wavelengths of light, such as violet and blue, more effectively than longer wavelengths. This scattering is known as Rayleigh scattering, and it causes the sky to appear predominantly blue to our eyes. ]

Question : Which of the following statements is correct regarding the propagation of light of different colours of white light in air?

(a) Red light moves fastest

(b) Blue light moves faster than green light

(d) Yellow light moves with the mean speed as that of the red and the violet light

Answer : (c) All the colors of white light move with the same speed.

[ In air (or a vacuum), all colors of light, including red, blue, green, etc., travel at the same speed, which is the speed of light. The speed of light is constant in a given medium and is approximately 3 x 10^8 meters per second in a vacuum.]

Question : 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

(d) moves fastest in air

Answer : (b) is scattered the least by smoke or fog.

[ Red light has longer wavelengths compared to blue light, and longer wavelengths tend to scatter less in the presence of particles like smoke or fog. Therefore, red light is more effective at penetrating through such atmospheric conditions, making it more visible from a distance.]

Question : Which of the following phenomena contributes significantly to the reddish appearance of the sun at sunrise or sunset?

(a) Dispersion of light

(b) Scattering of light

(d) Reflection of light from the earth

Answer : (b) Scattering of light.

[ The reddish appearance of the sun at sunrise or sunset is primarily due to the phenomenon of scattering of light. ]

Question : The bluish colour of water in deep sea is due to

(a) the presence of algae and other plants found in water

(b) reflection of sky in water

(d) absorption of light by the sea

Answer : (b) reflection of the sky in water.

[ The bluish color of water in the deep sea is primarily due to the selective absorption and scattering of sunlight. The water absorbs colors in the red part of the light spectrum, and the blue light is scattered in all directions. Additionally, the reflection of the sky in the water contributes to the overall bluish appearance. So, both scattering of light and the reflection of the sky play a role, but the reflection of the sky is a more direct contributor to the blue color. ]

Question : When light rays enter the eye, most of the refraction occurs at the

(a) crystalline lens

(b) outer surface of the cornea

(d) pupil

Answer : (b) outer surface of the cornea.

[ When light rays enter the eye, the majority of the refraction occurs at the outer surface of the cornea. The cornea is the transparent front part of the eye that plays a significant role in focusing light onto the retina.]

Question : The focal length of the eye lens increases when eye muscles

(a) are relaxed and lens becomes thinner

(b) contract and lens becomes thicker

(d) contract and lens becomes thinner

Answer : (a) are relaxed and the lens becomes thinner.

[ When the eye muscles are relaxed, the lens becomes thinner, and this increases its focal length. This adjustment allows the eye to focus on distant objects.]

Question : Which of the following statement is correct?

(a) A person with myopia can see distant objects clearly

(b) A person with hypermetropia can see nearby objects clearly

(d) A person with hypermetropia cannot see distant objects clearly

Answer : (c) A person with myopia can see nearby objects clearly.

[ Myopia, also known as nearsightedness, is a refractive error where distant objects appear blurry, but nearby objects can be seen more clearly.]