Case Study MCQ Questions Chapter 11 Human Eyes and Colourful World Class 10 Science

Please see below Case Study MCQ Questions Chapter 11 Human Eyes and Colourful World Class 10 Science. These MCQ Questions with Answers for Case study have been designed as per the latest syllabus and examination guidelines of Class 10 Science. Cased Study Based MCQ Questions for Class 10 Science are expected to come in the upcoming exams. We have provided a lot of case studies for all chapters in standard 10 science. Please solve the MCQ Questions and compare with the answers provided by our teachers.

Chapter 11 Human Eyes and Colourful World Class 10 Science Case Study MCQ Questions

The human eye is spherical in shape and has diameter of about 2.5 cm. Sclerotic is a tough, opaque and white substance forming the outermost coating of the eyeball. The front portion is sharply curved and covered by a transparent protective membrane called the ‘cornea’. Inner to the sclerotic there is a layer of black tissue called as choroids consisting of a mass of blood vessels, which nourishes the eye. The black colour does not reflect the light and hence rules out the blurring of image by reflection within the eyeball.
Behind the cornea, the space is filled with a liquid called theaqueous humour and behind that a crystalline lens. ‘Iris’ is a  muscular diaphragm lying between the aqueous humour and the crystalline lens. Iris has an adjustable opening in the middle called the pupil of the eye. The pupil appears black because all the light entering is absorbed by the ‘retina’, which covers the inside of the rear part of the ball. Iris controls the amount of light entering because the retina absorbs nearly all the light, which falls upon it. This is done by varying the aperture of the pupil with the help of the iris. In dim light the iris dilates the pupil so that more light can enter in. When the light is bright the pupil contracts. The crystalline lens divides the eyeball into two chambers. The chamber between the cornea and the lens is called the anterior chamber filled with a fluid called aqueous humour while the chamber between the lens and the retina is called the posterior chamber which is filled with a transparent gelatinous substance called vitreous humour. The refractive indices of the cornea, pupil lens and fluid portion of the eye are quite similar. So, when a ray of light enters the eye, it is refracted at the cornea. This refraction produces a real inverted and diminished image of distant objects on the retina.
When the object is kept at different distances then, we may expect the image to be formed at different distances from the lens. It means, it may not form on the retina always. But in reality it is not so. Image is always formed on the retina. This is possible because the curvature of the crystalline lens is altered by ciliary muscles. When the eye is focused on infinity the muscles are relaxed and the eye lens remains thin. If the object is brought near by, the curvature increases so that the image can be formed on the retina. This property of the eye lens is called accommodation.

Question. The change in focal length of an eye lens to focus the image of objects at varying distances is done by the action of _______
(a) pupil
(b) ciliary muscles
(c) retina
(d) blind spot

Question. The fluid between the retina and the lens is called ______
(a) aqueous humour
(b) vitreous humour
(c) aqua
(d) humus

Question. The part of the eye where optic nerves enter the eye 
(a) pupil
(b) ciliary muscles
(c) retina
(d) blind spot

Question. The inner back surface of the eyeball is called 
(a) pupil
(b) ciliary muscles
(c) retina
(d) blind spot

The phenomenon of decomposition of the white light into its seven component colours when passing through a prism or through a transparent object delimited by non parallel surfaces is called dispersion of light. A beam of light containing all the visible spectrum of the light is white, because the sum of all the colors generates the white color. The light is decomposed in all the component colours, Violet, Indigo, Blue, Green, Yellow, Orange and Red, called as VIBGYOR. The band of the coloured components of a light beam is called its spectrum. The phenomenon can be explained by thinking that light of different colours (different wavelengths) has different velocities while travelling in a medium vm = f λm. Hence, the change in velocity of light observed when the light passes from the air to the glass, depends on the wavelength.

Question. When white light is allowed to pass through a glass prism, which colour deviates the most? 
(a) Indigo
(b) Green
(c) Red
(d) Violet

Question. For a prism material, refractive index is highest for 
(a) Red
(b) Yellow
(c) Orange
(d) Violet 

Question. When white light is allowed to pass through a glass prism, which colour deviates the least?   
(a) Violet
(b) Red
(c) Green
(d) Orange

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. In which of the following cases, after dispersion, the third colour from the top corresponds to the colour of the sky? 

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
(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

Dispersion is the splitting up of white light into seven colours on passing through a transparent medium like a glass prism. When a white light beam is passed through a prism, a band of seven colors are formed is known as spectrum of white light as shown in given figure. When white light consisting of seven colors falls on a transparent medium (glass prism), each color in it is refracted (or deviated) by a different angle, with the result that seven colors are spread out to form a spectrum.

Question. Which of the following colour of white light is least deviated by the prism?
(a) green
(b) violet
(c) indigo
(d) yellow

Question. A beam of white light falls on a glass prism. The colour of light which undergoes the least bending on passing through the glass prism is:
(a) violet
(b) red
(c) green
(d) blue

Question. The splitting up of white light into seven colours on passing through a glass prism is called:
(a) refraction
(b) deflection
(c) dispersion
(d) scattering

Question. The colour of white light which is deviated the maximum on passing through the glass prism is:
(a) blue
(b) indigo
(c) red
(d) orange

Question. The colour of white light which suffers the maximum bending (or maximum refraction) on passing through a glass prism is:
(a) yellow
(b) orange
(c) red
(d) violet

Atmosphere refraction is the phenomenon of bending of light on passing through earth’s atmosphere. As we move above the surface of earth, density of air goes on decreasing. Local conditions like temperature etc. also affect the optical density of earth’s atmosphere. On account of refraction, stars seen appear higher than they actual are; advanced sunrise; delayed sunset, oval appearance of the sun at sunrise and sunset; stars twinkle, planets do not.

Question. In absence of atmosphere, the colour of sky appears
(a) blue
(b) black
(c) red
(d) yellow

Question. The sun appears oval shaped or flattened due to
(a) dispersion
(b) scattering
(c) atmospheric refraction
(d) cannot say

Question. Twinkling of stars and non-twinkling of planets is accounted for by
(a) Scattering of light
(b) dispersion of light
(c) atmospheric refraction
(d) none of these

Question. Due to atmospheric refraction, apparent length of the day
(a) increases
(b) decreases
(c) remains the same
(d) all of these

Question. Apparent position of the star appears raised due to
(a) atmospheric refraction
(b) scattering of light
(c) both (a) and (b)
(d) none of these

The twinkling of a star is due to atmospheric refraction of starlight. The starlight on entering the earth’s atmosphere, undergoes refraction continuously before it reaches the earth. The atmospheric refraction occurs in a medium of gradually changing refractive index. Since the atmosphere bends starlight towards the normal, the apparent position of the star is slightly different from its actual position. The star appears slightly higher than its actual position when viewed near the horizon. Further this apparent position of the star is not stationary, but keeps on changing slightly, since the physical conditions of the earth’s atmosphere are not stationary. Since the stars are very distant they are approximate pointsized source of light. As the path of rays of light coming from the star goes on varying slightly, the apparent position of the star fluctuates and the amount of starlight entering the eye flickers the stars sometimes appear brighter and at some other time, fainter, which is the twinkling effect.

Question. At noon, the Sun appears white as:
(a) Light is least scattered.
(b) All the colours of the white light are scattered away.
(c) Blue colour is scattered the most.
(d) Red colour is scattered the most.

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 with the fastest speed.
(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.

Question. The stars seem higher than they actually are due to:
(a) Reflection of light
(b) Refraction of light
(c) Scattering of light
(d) Inference of light

Question. Which of the following phenomenon of light is involved in the formation of rainbow?
(a) Reflection, refraction and dispersion
(b) Refraction, dispersion and total internal reflection.
(c) Refraction, dispersion and internal reflection.
(d) Dispersion, scattering and total internal reflection.

Question. Stars appear to twinkle because of:
(a) Atmospheric refraction
(b) Movement of air
(c) Both (a) and (b)
(d) None of these

A prism is a transparent refracting medium bounded by two plane surfaces inclined to each other at a certain angle. The refraction of light through a prism, follows the laws of refraction. In the prism refraction takes place on its refracting surface it means when the light enters the prism and when the light leaves the prism. The refraction through a prism is shown. Here A is the angle of prism, ∠i is the angle of incidence of the face AB and ∠e is the angle of emergence at other face AC. The incident ray suffers a deviation or bending through an angle δ due to the refraction through prism. This angle is called angle of deviation as shown in figure.

∠i + ∠e = ∠δ + ∠A

Question. When a ray is refracted through a prism, then
(a) ∠i = ∠δ
(b) ∠i = ∠e + ∠δ
(c) ∠ = ∠e
(d) ∠i > ∠r

Question. The rectangular surfaces of a prism are know as:
(a) reflecting surfaces
(b) dispersing surfaces
(c) refracting surfaces
(d) none of these

Question. The angle of deviation depends on
(a) refraction index of prism
(b) angle of incidence
(c) both (a) and (b)
(d) none of these

Question. The angle between the two refracting surfaces of a prism is called ____________.
(a) angle of prism
(b) angle of incidence
(c) angle of deviation
(d) angle of emergence

Question. The angle between the incident ray and the emergent ray is called ____________.
(a) angle of emergence
(b) angle of deviation
(c) angle of incidence
(d) none of these

The spreading of light by the air molecules is called scattering of light. The light having least wavelength scatters more. The sun appears red at sunrise and sunset, appearance of blue sky it is due to the scattering of light. The colour of the scattered light depends on the size of particles. The smaller the molecules in the atmosphere scatter smaller wavelengths of light. The amount of scattering of light depends on the wavelength of light. When light from sun enters the earth’s atmosphere, it gets scattered by the dust particles and air molecules present in the atmosphere. The path of sunlight entering in the dark room through a fine hole is seen because of scattering of the sun light by the dust parties present in its path inside the room.

Question. The colour of sky appears blue, it is due to the
(a) refraction of light through the atmosphere
(b) dispersion of light by air molecules
(c) scattering of light by air molecules
(d) all of these

Question. To an astronaut in a spaceship the colour of earth appears
(a) red
(b) blue
(c) white
(d) black

Question. The danger signs made red in colour, because
(a) the red light can be seen from farthest distance
(b) the scattering of red light is least
(c) both (a) and (b)
(d) none of these

Question. At the time of sunrise and sunset, the light from sun has to travel through ____________.
(a) longest distance of atmosphere
(b) shortest distance of atmosphere
(c) both (a) and (b)
(d) can’t say

Question. At the time of sunrise and sunset
(a) Blue colour scattered and red colour reaches our eye.
(b) Red colour scattered and blue colour reaches our eye.
(c) Green and blue scattered and orange reaches our eye.
(d) None of these.

The ciliary muscles of eye control the curvature of the lens in the eye and hence can alter the effective focal length of the system. When the muscles are fully relaxed, the focal length is maximum. When the muscles are strained the curvature of lens increases (that means radius of curvature decreases) and focal length decreases. For a clear vision the image must be on retina. The image distance is therefore fixed for clear vision and it equals the distance of retina from eye-lens. It is about 2.5 cm for a grown-up person. A person can theoretically have clear vision of objects situated at any large distance from the eye. The smallest distance at which a person can clearly see is related to minimum possiblefocal length. The ciliary muscles are most strained in this position. For an average grown-up person minimum distance of object should be around 25 cm. A person suffering for eye defects uses spectacles (Eye glass). The function of lens of spectacles is to form the image of the objects within the range in which person can see clearly. The image of the spectacle-lens becomes object for eye-lens and whose image is formed on retina.
The number of spectacle-lens used for the remedy of eye defect is decided by the power of the lens required and the number of spectacle-lens is equal to the numerical value of the power of lens with sign. For example power of lens required is +3D (converging lens of focal length 100/3 cm) then number of lens will be +3.
For all the calculations required you can use the lens formula and lens maker’s formula. Assume that the eye lens is equiconvex lens. Neglect the distance between eye lens and the spectacle lens.

Question. A nearsighted man can clearly see object only upto a distance of 100 cm and not beyond this. The number of the spectacles lens necessary for the remedy of this defect will be 
(a) +1 D
(b) –1 D
(c) + 3 D
(d) – 3 D

Question. Minimum focal length of eye lens of a normal person is  
(a) 25 cm
(b) 2.5 cm
(c) 25/9 cm
(d) 25/11 cm

Question. Maximum focal length of eye lens of normal person is  
(a) 25 cm
(b) 2.5 cm
(c) 25/9 cm
(d) 25/11 cm