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Ray And Wave Optics Mcq
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Q.1
Chromatic aberration will be absent if for two thin lenses in contact
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a) (ω1 / f1 ) + (ω2 /f2)=0
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b)(ω1 / f2 ) + (ω2 /f1)=0
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c)(f1/ω2 ) + (f2.ω1 )=0
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d)(ω1+ω2) + (f1 + f2)=0
Explanation
Answer:(a)
Q.2
A thick plane mirror shows a number of images of the filament of an electric bulb. Of these the brightest is the
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a) First
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b) Second
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c) Third
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d) Last
Explanation
Answer: (b)
Q.3
The image formed by a convex mirror of focal length 20cm is half the size of the object. Then the distance of the object from the mirror is
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a)20 cm
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b) 10 cm
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c)30 cm
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d)60 cm
Explanation
Answer: (a)
Q.4
A light ray incident normally on plane mirror suffers a deviation of
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a) zero
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b) π/2
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c)π
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d)2π
Explanation
Answer: (c)
Q.5
A man stands in front of mirror with his hand at 03 m from the mirror. In order to see the image of the hand clearly the man must focus his eye at a distance of
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a) 0.3 m
0%
b) 0.45 m
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c)0.6 m
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d)0.75 m
Explanation
Answer:(c)
Q.6
A person wears glasses of power -2.0D. The defect of the eye and the far point of the person without the glasses will be [ MPPMT 1999]
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a) Nearsighted, 50cm cm
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b) Farsighted, 50cm
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c)Nearsighted, 250 cm
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d)Astigmatism, 50
Explanation
Answer:(a)
Q.7
An object is placed at a distance of 10cm from a concave mirror of radius of curvature 0.6m. Which of the following statements is incorrect?
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a)the image is formed at a distance of 15cm from the mirror
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b) the image formed is real
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c)the image is 1.5 times the size of the object
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d)the image formed is virtual and erect
Explanation
Answer: (b)
Q.8
The ray of different colours fail to converge at a point after going through a converging lens. This defect is called
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a) Spherical aberration
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b) distortion
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c) coma
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d) chromatic aberration
Explanation
Answer: (d)
Q.9
Chromatic aberration of lens can be corrected by
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a)Providing different suitable curvature of its two surfaces
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b) Proper polishing of its two surfaces
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c)Suitably combining it with another lens
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d)reducing its aperture
Explanation
Answer: (c)
Q.10
An achromatic combination of lenses produces
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a) Image in black and white
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b) coloured images
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c)Images unaffected by variation of refractive index with wavelength
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d)highly enlarged images
Explanation
Answer: (c)
Q.11
The size of an object as perceived by an eye depends primarily on
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a) actual size of the object
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b) distance of the object from eye
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c)aperture of the pupil
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d)size of the image formed on the retina
Explanation
Answer:(d)
Q.12
The magnifying power of compound microscope in terms of the magnification mo due to objective and magnifying power me by the eye-piece is given by [ CET 1994]
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a)mo / me
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b) mo × me
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c)mo + me
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d)me / mo
Explanation
Answer: (b)
Q.13
A dentist has a small mirror of focal length 16mm. He views the cavity in the tooth of a patient by holding the mirror at a distance of 8mm from the cavity. the magnification is
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a) 1
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b) 1.5
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c)2
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d)3
Explanation
Answer: (c)
Q.14
Total internal reflection can occur when light passes from
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a) A denser to rarer medium
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b) A rare to denser medium
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c)One medium to another of equal refractive index
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d)One medium to another of equal absorption coefficient
Explanation
Answer: (a)
Q.15
When a plane mirror is placed horizontally on level ground at a distance of 60 metres from the foot of tower, the tower and its image in the mirror subtend at the eye an angle of 90°. the height of the tower is
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a) 30 m
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b) 90 m
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c) 60 m
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d) 120 m
Explanation
Answer: (c)
Q.16
Which of the following wave lengths is in infrared region [ EAMCET 1994]
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a) 5460 Å
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b) 5893 Å
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c)7000 Å
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d)4320 Å
Explanation
Answer: (c)
Q.17
The length of an astronomical telescope for normal vision is [ EAMCET 1995]
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a) fo × fe
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b) fo / fe
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c)fe / fo
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d)fo + fe
Explanation
Answer:(d)
Q.18
Which one of the wave can not be polarized? [ EAM CET 1994]
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a) Radio waves
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b) sound waves
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c)X-rays
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d)Ultraviolet rays
Explanation
Answer:(b)
Q.19
A plane mirror reflecting a ray of incident light is rotated through an angle θ about an axis through the point of incidence in the plane of the mirror perpendicular to the plane of incidence then
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a)the reflected ray does not rotate
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b) the reflected ray rotates through angle θ
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c)the reflected ray rotates through an angle 2θ
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d)the incident ray is rotates
Explanation
Answer: (c)
Q.20
A convex mirror is used to form an image of real object. Then tick the wrong statement
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a) the image lies between the pole and focus
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b) the image is diminished in size
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c)the image is erect
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d)the image is real
Explanation
Answer: (d)
Q.21
Sunlight filtering through a tree often makes circular patches on the ground because
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a) the space through which light penetrates is round
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b) the sun is round
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c)light is transmitted as wave motion
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d)Due to diffraction phenomenon
Explanation
Answer:(d)
Q.22
In a simple microscope, if the final image is located at infinity then its magnifying power
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a) 25/F
0%
b) 25/D
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c) F/25
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d) ( 1 +25/F)
Explanation
Answer: (a)
Q.23
An astronomical telescope has a length of 44 cm and ten fold magnification. The focal length of the objective lens is.. [ CBSE-PMT 1997]
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a) 4 cm
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b) 40 cm
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c)44 cm
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d)440 cm
Explanation
length of astronomical telescope (fo + fe)=44cm and magnification (fo / fe )=10From the given magnification, we find that fo=10×fe ∴ 10×fo + fe=44∴ fe=4 and fo=40cm Answer: (b)
Q.24
The ratio of angle of minimum deviation from a thin prim with respect to air and when dipped in water will be µg=3/2, µw=3/4 [ AFMC 1999]
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a) 1/3
0%
b) 1/4
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c)1/2
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d)1/8
Explanation
For thin prism, angle of minimum deviation δm=( µ-1) A In air δm=( µg-1) A In air δm=[(3/2)-1]A --eq(1) In water δm=( µgw-1) A Here µgw is refractive index of glass with respect to waterµgw=µg / µwµgw=(3/2) / (3/4)=2In water δm=(2-1)A=A --eq(2)taking ratio of eq(1) and eq(2) we get answer(c)Answer: (c)
Q.25
If the critical angle for total internal reflection from a medium to vacuum is 30°. Then velocity of light in the medium is ---{AFMC 1997]
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a)1.5×108 m/s
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b) 2×108 m/s
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c)3×108 m/s
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d)0.75 ×108 m/s
Explanation
µ=1 / sin c µ=1/ sin30µ=2 µ=velocity of light in vacuum / velocity of light in medium Velocity of light in medium=velocity of light in vacuum / µ Velocity of light in medium=3×108 / 2=1.5×108 Answer: (a)
Q.26
If the critical angle of medium of prism is C and the angle of prism is A, then there will be no emergent ray when
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a) A < 2C
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b) A=2C
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c)A > 2C
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d)A ≥ 2C
Explanation
Answer:(c)
Q.27
The diameter of the object lens of telescope is 5.0 m and wavelength of light is 6000 Å . The limit of resolution of this telescope is [AFMC 1997]
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a) 0.15 sec
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b) 0.06 sec
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c)0.03sec
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d)3.03 sec
Explanation
Angular limit of resolution=1.22λ / D Angular limit of resolution=1.22×6000×10-10 / 5 Angular limit of resolution=1464 ×10-10 rad1 rad=(360)(600)60)/2π sec=2.06× 105∴ Angular limit of resolution=0.03 sec Answer:(c)
Q.28
Two lenses have powers +D and -2D respectively. The power of combination is ..[AFMC 1998]
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a) +2D
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b) -3D
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c) -D
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d) +D
Explanation
The power of combination=D-2D=-D Answer: (c)
Q.29
A ray of light is incident on the surface of separating two transparent medium at an angle 45° and is refracted in medium at an angle 30°. Velocity of light in the medium will be..[ AFMC 1998]
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a)3.8×108 m/s
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b) 3.38×108 m/s
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c)2.12×108 m/s
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d)1.5×108 m/s
Explanation
According to Snell's Law here 'i' is angle of incidence=45°, 'r' is angle of refraction=30°'c' velocity of light in air=3×108and 'v' velocity of light in mediumsubstituting values in above equation we getAnswer: (c)
Q.30
A ray of light is incident on a glass plate at an angle of 60°. What would be the refractive index of glass if reflected and refracted rays are perpendicular to each other? [ AFMC 1998]
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a) √3
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b) 3/2
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c)√3 / 2
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d)1/2
Explanation
As reflected and refracted rays are perpendicular from figure Angle of refraction=180-i-90r=180-60-90=30° Answer: (a)
Q.31
If red light and violet light rays are of focal length fR and fv respectively then which one of the following is true..[ AFMC 1999]
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a)λR ≤ λv
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b)µR > µv
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c)µR=µv
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d)µR < µv
Explanation
red light deviates less than violet light thus µR < µv Answer:(d)
Q.32
The objective with large aperture are used in telescope for [ AFMC 2000]
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a) ease of manufacture
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b) reducing lens aberration
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c) greater resolution
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d) bright image
Explanation
Larger the aperture of the telescope, greater will be the resolutionAnswer: (c)
Q.33
Light from a denser medium I goes to rarer medium II. When angle of incidence is θ, the reflected and refracted rays are perpendicular to each other. The critical angle is [ AFMC 2000]
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a)sin-1(cos θ)
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b) sin-1(cot θ)
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c)sin-1(tan θ)
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d)sin-1(1)
Explanation
light is travelling from denser medium refractive index 'n12’ then sinθ/ sin r= n2/n1 From figure r=90-θ sinθ/sin(90-θ)= n2/n1 sinθ/cosθ= n2/n1 ∴ tanθ= n2/n1 For critical angle sinC= n2/n1 tanθ=sinC C = sin-1tanθ Answer: (c)
Q.34
A point object is 24 cm above the surface of water (µ=4/3) in lake. A fish inside the water will observe the image to be at a point [ AFMC 2001]
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a) 6cm above the surface of water
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b) 6cm below the surface of water
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c)18 cm above the surface of water
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d)32 cm above the surface of water
Explanation
we will use following equationhere n1 is the refractive index of medium of observer in our case it is fish=4/3hi apparent height of image observed by fishn2 is refractive index of medium in which object is=1 (air)ho is actual height of object=24cmsubstituting values in above equation we get(4/3)/ 1=hi/24h i=32cm above the surface of waterAnswer: (d)
Q.35
The optical length of an astronomical telescope with magnifying power of 10, for normal vision is 44cm. What is focal length of the objective? [ AFMC 2001]
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a) 4cm
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b) 40 cm
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c)44cm
0%
d)440 cm
Explanation
Optical length=fo + fe 44=fo + fe magnifying power=fo / fe 10=fo / fe10 ×fe=fo ∴ 44=10 ×fe + fe fe=4 cmfo=40cm Answer:(b)
Q.36
An optician prescribes spectacles to a patient with a combination of convex lens of focal length 40cm and concave lens 25cm. The power of spectacles is ...[ AFMC 2002]
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a) 6.0 D
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b) 1.5 D
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c) -6.0 D
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d) -1.5 D
Explanation
The formula for power of combination of lenses is P=P1 + P2 P=1/ f1 + 1/f2 P=1/0.4 + 1/(-0.25) P=2.5 - 4 P=-1.5 D Answer: (d)
Q.37
Ray optics is valid, when characteristic dimensions are... [ CBSE-PMT 1989]
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a) of the same order as the wavelength of light
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b) much smaller than the wavelength of light
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c) of the order of one millimeter
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d) much larger than the wavelength of light
Explanation
Answer: (d)
Q.38
The frequency of light wave in material is 2×1014Hz and wavelength is 5000Å. The refractive index of material will be... [ CBSE-PMT 2007]
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a) 1.50
0%
b) 3.00
0%
c) 1.33
0%
d) 1.40
Explanation
According to equation velocity of light in medium v =fλ here f is the frequency f = 2×1014 Hz λ = 5000Å =5000×10-10 m v = 2×1014 ×5000×10-10 v = 108 m/s Refractive index of material µ = c/v = 3×108 / 108 = 3 Answer: (b)
Q.39
A biconvex lens has a radius of curvature of magnitude 20cm. Which one of the following options best describe the image formed of object of height 2cm placed 30cm from the lens?
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a) Virtual, upright, height = 1cm
0%
b) Virtual, upright, height = 0.5cm
0%
c) Real, inverted, height = 4cm
0%
d) Real, inverted, height = 1cm
Explanation
Focal length of lens depends on the refractive index of lens , medium in which it is kept,and Radius of curvature. According to lens formula Now magnification m = hi / ho = v/u hi = (v/u)×ho hi = {60/(-30)}2 = -4cm Negative sign indicates real inverted image Answer:(c)
Q.40
A converging beam of ray is incident on a diverging lens. Having passed through the lens the ray intersect at point 15cm from the lens on the opposite side. If the lens is removed the point where the ray meet will move 5cm closer to the lens. The focal length of the lens is .. [ CBSE-PMT 2011]
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a) -10 cm
0%
b) 20 cm
0%
c) -30cm
0%
d) 5 cm
Explanation
converging lens will form image at 15cm after passing through the divergent lance When divergent lenses is removed image is formed closer to lens by 5cm Thus image formed by convergent lens is at 15cm-5cm=10cm=u Final image is formed at v=15cm Substituting values in lens formula we get f=-30cm Answer: (c)
Q.41
A convex lens and a concave lens, each having same focal length of 25cm, are put in contact to form a combination of lenses. The power in diopters of the combination is .. [ CBSE-PMT 2006]
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a)50
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b) infinite
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c)zero
0%
d)25
Explanation
since lenses have equal but opposite signs hence power=0Answer: (c)
Q.42
Which of the following is not due to total internal reflection? [ CBSE-PMT 2011]
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a) Working of optical fiber
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b) Difference between apparent and real depth of pond
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c)Mirage on hot summer days
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d)Brilliance of diamond
Explanation
Difference between apparent and real depth of s pond is due to the refraction of light, not due to the total internal reflection. Other three phenomena are due to the total internal reflection of lightAnswer: (b)
Q.43
A boy is starting a fire by focusing sunlight on a piece of paper using an equiconvex lens of focal length 10cm. The diameter of sun is 1.39×109m and its mean distance from the earth is 1.5×What is the diameter of the Sun's image on the paper? .. [ CBSE-PMT 2008]
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a)9.2×10-4
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b) 6.5×10-4
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c)6.5×10-5
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d)12.4×10-4
Explanation
We know magnification m=v/u=h0 / hiThus size of image hi=(v/u)×ho Answer:(a)
Q.44
A convex lens of focal length 80cm and a concave lens of focal length 50cm are combined together. What will be their resulting power? [CBSE-PMT 1996]
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a) +6.5D
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b) -6.5D
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c) +7.5D
0%
d) -0.75D
Explanation
here f1=80cm and f2=-50cm Answer: (d)
Q.45
A ray of light traveling in a transparent medium of refractive index μ, falls on a surface separating the medium from air at an angle of incidence of 45°. For which of the following values of μ the ray can undergo total internal reflection? [ CBSE-PMT 2010]
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a)1.33
0%
b) 1.40
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c)1.50
0%
d)1.25
Explanation
For total internal reflection, µ ≥ 1 / sinCµ ≥ 1 / sin45µ ≥ √2 µ ≥ 1.414 ≅ 1.5Answer: (c)
Q.46
Monochromatic light is the light in which
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a)single wavelength is present
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b) Various wavelengths are present
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c)Red and violet light is present
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d)Yellow and red light is present
Explanation
Answer: (a)
Q.47
Two independent mono-chromatic sources of light are
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a) coherent
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b) incoherent
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c)coherent or incoherent depending up on the nature of source
0%
d)None of the above
Explanation
Answer: (b)
Q.48
A thin prism of angle 15° made of glass of refractive index μ1=1.5 is combined with another prism of glass of refractive index μ2=1.The combination of the prism produces dispersion without deviation. The angle of the second prism should be [ CBSE-PMT 2011]
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a) 7°
0%
b) 10°
0%
c)12°
0%
d)5°
Explanation
Deviation is zeroso δ=δ1 + δ2=0⇒ (µ1-1)A1 + (µ2 -1)A2=0 ∴ (1.5-1)15=-(1.75-1)A2∴ A2=-10° Negative sign shows that the second prism is inverted with respect to the first.Answer: (b)
Q.49
light enters at an angle of incidence in a transparent rod of refractive index n. For what value of the refractive index n. For what value of the refractive index of the material of rod the light once entered into it will not leave it through its lateral face whatsoever be the value of angle of incidence? [ CBSE-PMT 1998]
0%
a) n > √2
0%
b) n=1
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c)n=1.1
0%
d)n=1.3
Explanation
Let ray of light enters at A and the refracted beam is AB. This is incident at an angle θ. For no refraction at the lateral face θ >C. Or sinθ > sinC. But θ + r=90° θ=90° - r∴ sin(90° - r ) > sinC Or cos r > sinC eq(1) Now according to Snell's law n=sin i / sin r sin r=sin i/n from trigonometric identity ∴ from equation 1Also sinC=1/nMaximum value of sini=1∴ n2 > 2n > √ 2 Answer:(a)
Q.50
The refractive index of the material of the prism is √3 ; Angle of prism is 60° then the angle of minimum deviation of the prism is.. [ CBSE-PMT 1999]
0%
a) 30°
0%
b) 45°
0%
c) 60°
0%
d) 75°
Explanation
Angle of minimum deviation Answer: (c)
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