CBSE Questions for Class 12 Medical Physics Ray Optics And Optical Instruments Quiz 6 - MCQExams.com

The near point of a long sighted person is 40 cm from the eye. To read a book held at a distance of 25 cm, he will need spectacles containing 
  • Chromatic lenses
  • Prismatic lenses
  • Concave lenses
  • Convex lenses
The term refraction of light is best described by:
  • The bending of light rays when they enter from one medium to another medium
  • Splitting of white light into seven colours when it passes through the prism
  • Bending of light round corners of obstacles and apertures
  • Coming back of light from a bright smooth surface
A man can read the number of a distant bus clearly but is not able to read a book clearly. Which defect of the eye is he suffering from?
  • Myopia
  • Hypermetropia
  • Cataract
  • Astigmatism
A person cannot see objects clearly which are nearer than 75 cms from his eyes, the disease he is suffering from is:
  • Astigmatism
  • Myopia
  • Hypermetopia
  • Presbyopia
Twinkling of stars is on account of
  • Large distance of stars and storms in air
  • Small size of stars
  • Large size of stars
  • Large distance of stars and fluctuations in the density of air
The ratio of the size of the image to the size of the object is known as :
  • The Focal Plane
  • The Transformation ratio
  • The Efficiency
  • The Magnification ratio
The twinkling of stars is due to atmospheric
  • Refraction of light
  • Reflection of light
  • Scattering of light
  • Dispersion of light
A convex lens magnifying glass is of-
  • Long focal length
  • Short focal length
  • Very long focal length
  • All the above
The film of camera is compared to which part of human eye?
  • Lens
  • Retina
  • Iris
  • Choroid
A mirage occurs because
  • The refractive index of atmosphere increases with height
  • The refractive index of atmosphere decreases with height
  • The hot ground acts like a mirror
  • Refractive index remains constant with height
Twinkling of stars is due to
  • variation of refractive index in the earth's atmosphere
  • the fact that light is not emitted by the stars continuously
  • the absorption oflight by earth's atmosphere
  • none of these
Figures (a), (b), (c) and (d) respectively correspond to 
369632_25e33fe7c53b46d28feb68538da4c4cc.png
  • 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
The figure above shows the eye suffering from :
369938_d4c1e4cac0494731b28df81fa1dc2364.jpg
  • hypermetropia
  • myopia
  • astigmatism
  • short-sightedness
Which of the following lens is used to minimise hypermetropia ?
  • Convex lens
  • Concave lens
  • Cylindrical lens
  • Planar lens
Long-sightedness is to hypermetropia as short-sightedness is to :
  • myopia
  • focusing
  • astigmatism
  • accomodation
Figure (a), (b), and (c) respectively, indicate the point of focus in case of :
369648_6f6772b65d5f4f4ebd85c0fa90b2c2e5.png
  • 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
Long-sightedness is caused by the eyeball being too short. It can be corrected by the use of a :
  • convergent lens
  • plane mirror
  • divergent lens
  • concave mirror
The figure above shows the eye suffering from :
369948_badaff3cd80b41cfbf72cf9457172f25.png
  • hypermetropia
  • myopia
  • astigmatism
  • far-sightedness
Hypermetropia is due to the ________ of the eye.
  • low converging power
  • low diverging power
  • high converging power
  • high diverging power
When the light is very bright,
  • The iris makes the pupil expand
  • The iris makes the pupil contract
  • The iris and the pupil remain as they are
  • The iris and the pupil damages 
The bending of light ray after passing through a medium is commonly known as :
  • Refraction
  • Scattering
  • Reflection
  • Interference
Which of the following lens is used to minimise myopia ?
  • Convex lens
  • Concave lens
  • Cylindrical lens
  • Planar lens
State whether true or false :
Myopia is caused due to the high converging power of the eye lens.
  • True
  • False
The sky is blue because
  • There is more blue light in the sunlight
  • Of scattering of sunlight by air molecules in the atmosphere
  • Of scattering of sunlight by dust particles in the atmosphere
  • Other colours are absorbed by heavenly bodies
Which of the following is not a characteristics of a concave lens?
  • Thick at the edges and thin in the middle.
  • Used to correct shortsightedness
  • A diverging lens
  • Used to correct longsightedness
The relation between $$u, v$$ ( u is the object distance and v is the image distance )  and f for mirror is given by:
  • $$\displaystyle f=\frac{uv}{u-v}$$
  • $$\displaystyle f=\frac{2u\times v}{u+v}$$
  • $$\displaystyle f=\frac{u\times v}{u+v}$$
  • none of these
In hypermetropia, the image of near object is formed :
  • Before the retina
  • On retina
  • Behind the retina
  • Above the retina
In myopia, the image of distant object is formed :
  • Before the retina
  • On the retina
  • Behind the retina
  • Above the retina
An object (O) is placed in a medium M of refractive index 5/A convex lens of focal length 15 cm is placed in front of the object as shown in the figure.  Determine the position of the image formed by the lens.  
394968.JPG
  • 15 cm
  • 20 cm
  • 30 cm
  • 60 cm
An astronomical telescope has an eyepiece of focal length $$5 cm$$. If magnification produced is $$14$$ in normal adjustment, then what is the length of telescope?
  • $$25 cm$$
  • $$75 cm$$
  • $$50 cm$$
  • $$100 cm$$
Choose the correct relation between u, v and r for a spherical mirror:
  • $$\displaystyle r=\frac{2uv}{u+v}$$
  • $$\displaystyle r=\frac{2}{u+v}$$
  • $$\displaystyle r=\frac{2(u+v)}{(uv)}$$
  • $$\displaystyle r=\frac{uv}{u+v}$$
A lens is made of flint glass (refractive index = 1.5). When the lens is immersed in a liquid of refractive index 1.25, the focal length :
  • Increases by a factor of 1.25
  • Increases by a factor of 2.5
  • Increases by a factor of 1.2
  • Remains same 
A thin glass (refractive index 1.5) lens has optical power of $$-5 D$$ in air. Its optical power in a liquid medium with refractive index 1.6 will be: 
  • $$-1D$$
  • $$1D$$
  • $$-25D$$
  • $$25D$$
The sun appears red at the time of sun-rise and sun-set. This is because:
  • red colour is least scattered
  • red colour is most scattered
  • the sun is red in colour
  • our eyes can sense only red colour
LASER belongs to the range of
  • Infrared rays
  • Visible light
  • UV rays
  • X-rays
In an electron microscope the accelerating voltage is increased from 20 kV to 80 kV, the resolving power ofthe microscope will become.
  • 2R
  • $$\frac {2}{R}$$
  • 4R
  • 3R
Why does sun appear reddish at sunrise and sunset?
  • Near the horizon it passes through thick layers of atmosphere having larger particles
  • Sunlight travels longer distance at sunrise and sunset
  • Both A and B
  • None of the above
Assertion: A double convex lens ($$\mu$$ = 1.5) has focal length 10 em, When the lens is immersed in water ($$\mu$$ = 4/3) its focal length becomes 40 cm.
Reason: $$\frac{1}{f}=\frac{\mu_1-\mu_m}{\mu_m}=\left ( \frac{1}{R_1}-\frac{1}{R_2} \right )$$.
  • Both assertion and reason are true but the reason is the correct explanation of assertion
  • Both assertion and reason are true but the reason is not the correct explanation of assertion
  • Assertion is true but reason is false
  • Both the assertion and reason are false
  • Reason is true but assertion is false
Sodium lamps are used in foggy conditions because:
  • yellow light is scattered less by the fog particles
  • yellow light is scattered more by' the fog particles
  • yellow light is unaffected during its passage through the fog
  • Wavelength of yellow light is the mean of the visible part of the spectrum
A defect of vision caused due to excessive curvature of the cornea is:
  • myopia
  • hypermetropia
  • astigmatism
  • presbyopia
A person who is near sighted will have the most trouble reading
  • a newspaper in his hands
  • a mobile screen in front of him
  • a street sign across the street
  • the menu in a restaurant
Match the following
i. Corneaa. Back surface of eye where image is formed
ii. Pupilb. Coloured part of eye
iii. Retinac. Membrane that refracts light and protects the eye
iv. Irisd. Transparent opening of eye.Light passes through it
 
  • i-c ,ii-d,iii-a,iv-b
  • i-a,ii-c,iii-b,iv-d
  • i-d,ii-a,iii-b,iv-c
  • i-b,ii-c,iii-d,iv-a
If a person can see an object clearly when it is placed at about $$25 cm$$ away from him, he is suffering from:
  • myopia
  • hypermetropia
  • astigmatism
  • none of these
Long sightedness happens as:
  • ciliary muscles tighten
  • ciliary muscles weaken
  • eyeball size does not change
  • all the above happen
Bi-focal lens is required to correct:
  • cataract
  • astigmatism
  • myopia
  • presbyopia
Match the column:

a. optic nervei. coloured part of the eye
b. ciliary muscleii. refracts light and focuses a real image on the back of eye
c. lensiii. it can increase or decrease the thickness of lens
d.irisiv. carries information to the brain about light that strikes the retina
  • a-i,b-iii,c-iv,d-ii
  • a-ii,b-i,c-iv,d-iii
  • a-iii,b-iv,c-i,d-ii
  • a-iv,b-iii,c-ii,d-i
Near point of an eye suffering from long-sightedness is:
  • less than 25cm
  • greater than 25cm
  • equal to 25cm
  • infinity
A girl viewed an object and found that it is not clearly visible to her. It was found that the image was formed by her eye lens $$3cm$$ away from the pupil of her eyes.The girl can correct this defect by using a:
  • concave lens
  • convex lens
  • bi-focal lens
  • plano-convex lens
Why does the sky appear blue?
  • The color of water is reflected on the sky
  • Fine particles in the atmosphere scatter light of shorter wavelength
  • The water molecules in the atmosphere makes the sky appear blue
  • None of these
Select the correct alternative
A ray of light moving from an optically rarer to a denser medium 
  • Bends away from the normal
  • Bends towards the normal
  • Remains undeviated
  • None of the above
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