Q.1
Two lenses in contact form an achromatic doublet. Their focal lengths are in ratio 2 : 3 then their dispersive power must be in ratio [ Raj. PMT 1997]
  • a) 2:3
  • b) 1:3
  • c) 3:1
  • d) 3:2
Q.2
The focal length of thin convex lens for red and blue ray are 100cm and 98.8 cm respectively. The dispersive power of the material of the lens is [ MPPMT 1990]
  • a)0.968
  • b) 0.98
  • c)0.0325
  • d)0.325
Q.3
An achromatic convergent doublet of two lenses in contact has power of +2D. The convex lens has power +5D. What is the ratio of the dispersive power of the convergent and divergent lenses [ MPPMT 1990]
  • a) 2:5
  • b) 3:5
  • c)5:2
  • d)5:3
Q.4
A magnifying glass is to be used at the fixed object distance of 1 inch. If it is to produce an erect image magnified 5 times, its foal length should be [ MPPMT 1990]
  • a) 0.2 inch
  • b) 0.8 inch
  • c)1.25 inches
  • d)5.0 inches
Q.5
A certain far sighted person cannot see object closer to the eye than 100cm. The power of the lens which will enable him to read at a distance of 25cm will be [ MPPMT 1990]
  • a) 3 D
  • b) 1 D
  • c) 4D
  • d) 2D
Q.6
A film projector magnifies a 100 sq.cm film strip on a screen. If the linear magnification is 4, the area of the magnified film on the screen is [ CPMT 1991]
  • a)1600 sq cm
  • b) 400 sq.cm
  • c)800 sq.cm
  • d)200 sq.cm
Q.7
The magnifying power of a telescope isWhen it is adjusted for parallel rays, the distance between the objective and eye piece is found to be 20cm. The focal length of the lenses are [ MPPMT 1986]
  • a) 18cm, 2cm
  • b) 11cm, 9cm
  • c)10cm, 10cm
  • d)15cm, 5cm
Q.8
When the length of a microscope tube is increased, its magnifying power [ CPMT 1998]
  • a) decreases
  • b) increases
  • c)does not change
  • d)none of the above
Q.9
In order to increase the magnifying power of a microscope [ AFMC 1994]
  • a) The focal powers of the objective and eyepiece should be large
  • b) Objective should be have small focal length and eye-piece large
  • c) Both should have large focal length
  • d) The objective should have large focal length and eye-piece should have small
Q.10
Resolving power of telescope depends up on
  • a) the focal length and aperture of the eye lens
  • b) the focal lengths of the objective and the eye lens
  • c)the aperture of the objective and eye lens
  • d)the wavelength of light illuminating the object
Q.11
fv and fR the focal lengths of convex lenses for violet and red light respectively, and Fv and FR are the focal lengths of a concave lens for violet and red light, respectively. Which of the following relations is correct [ CPMT 1998]
  • a) fv < fR and Fv > FR
  • b) fv > fR and Fv < FR
  • c)fv < fR and Fv < FR
  • d)fv > fR and Fv > FR
Q.12
Four convergent lenses have focal lengths 100cm, 10cm, 4cm and 3cm. For telescope with maximum possible magnification, we choose the lenses of focal length [ CET 1994]
  • a) 100 cm, 3cm
  • b) 10 cm, 3cm
  • c)10cm, 4 cm
  • d)100cm, 4cm
Q.13
To increase the magnification of telescope
  • a) the objective lens should be of large focal length and eyepiece should be of short focal length
  • b) the objective and eye piece both should be of large focal lengths
  • c) both the objective and eyepiece should be of smaller lengths
  • d) the objective should be of small focal length and eyepiece should be of large focal length [ MPPMT 1994]
Q.14
Astigmatism can be corrected by using [ CBSE 1990]
  • a)Bifocal lenses
  • b) Concave spherical lenses
  • c)Plano-convex lenses
  • d)Cylindrical lenses
Q.15
When objects at different distances are seen by the eye which of the following remains constant? [ MPPMT 1999]
  • a) the focal length of the eye lens
  • b) the object distance from the eye lens
  • c)the radii of curvature of the lens
  • d)the image distance from the eye lens
Q.16
A man can see an object up to a distance of one metre from his eye. For correcting his eye sight so that he can see an object at infinity he requires a lens whose power is [ MPPMT 1993]
  • a) +0.5 D
  • b) +1.0 D
  • c) +.0D
  • d) -1D
Q.17
Chromatic aberration of lens is [ MPPMT 1989]
  • a)Not dependent on focal length
  • b) Directly proportional to focal length
  • c)Inversely proportional to focal length
  • d)Inversely proportional to dispersive power
Q.18
The focal lengths of objective and eye-lens of an astronomical telescope are respectively 2 metre and 5cm. Final image is formed at (1) least distance of distinct vision (2) infinity. Magnifying power in two cases will be [ MPPMT 19998]
  • a) -48, -40
  • b) -40, -48
  • c)-40, +48
  • d)-48, +40
Q.19
When seen in green light, the saffron and green portion of our National flag will appear to be [ UGET 1995]
  • a) black
  • b) black and green respectively
  • c)green and yellow respectively
  • d)green
Q.20
A fly is sitting on the objective of a telescope pointed towards the moon. What effect is expected in a photograph of the moon taken through the telescope [ MPPMT 1999]
  • a) the entire field of view is blocked
  • b) there is an image of the fly on the photographs
  • c) there is no effect at all
  • d) there is a reduction in the intensity of image
Q.21
Two parallel pillars are 11 km away from an observer. The minimum distance between the pillars so that they can be seen separately will be [ Raj.PET 1997]
  • a)3.2 m
  • b) 20.8
  • c)91.5 m
  • d)183 m
Q.22
The magnification is more than unity when object is placed at a distance d from a convex lens. Its focal length is 20cm. What is d? [ CPMT 1985]
  • a) Greater than 20cm
  • b) Less than 20cm
  • c)40 cm
  • d)Greater than 20cm but less than 40cm
Q.23
A person can not see object clearly beyond 2.0m. The power of lens required to correct his vision will be [ MPPMT 1998]
  • a) +2.0D
  • b) -1.0D
  • c)1.0D
  • d)-0.5D
Q.24
When diameter of the aperture of the objective of telescope is increased. its [ MPPMT 1997]
  • a) magnifying power is increased and resolving power decreased
  • b) magnifying power and resolving power both are increased
  • c) magnifying power remains the same but resolving power is increased
  • d) magnifying power and resolving power both are decreased
Q.25
A person is suffering from the defect astigmatism. Its main reason is that [ MPPMT 1994]
  • a)distance of the eye lens from retina is increased
  • b) distance of the eye lens from retina is decreased
  • c)the corona is not spherical
  • d)power of accommodation of the eye is decreased
Q.26
When the length of a microscope tube is increases, its magnifying power [ MNR 1986]
  • a) Decreases
  • b) Increases
  • c)Does not change
  • d)May increase or decrease
Q.27
The diameter of moon is 3.5×103 km and its distance from the earth is 3.8× 105km. The focal length of the objective and eye-piece as 4 metre ad 10cm respectively, the diameter of the image of the moon will be approximately [ CPMT 1991]
  • a) 2°
  • b) 20°
  • c)40°
  • d)50°
Q.28
The focal length of converging lens is measured for violet, green and red colours. It is respectively fv, fg, fr. We will find that
  • a) fv=fr
  • b) fv > fr
  • c) fv < fr
  • d) fg > fr
Q.29
Least distance of distinct vision is 25cm. Magnifying power of simple microscope of focal length 5cm is ..[ EAMCET 1995]
  • a)1/5
  • b) 5
  • c)1/6
  • d)6
Q.30
The focal lengths of the objective and the eye piece of a compound microscope are 2.0cm and 3.0 cm respectively. The distance between the objective and eye-piece is 15.0 cm. The final image is formed by eyepiece is at infinity. The two lenses are thin. The distances, in cm, of the objective measured from the objective lens, are, respectively [ IIT 1995]
  • a) 2.4 and 12.0
  • b) 2.4 and 15.0
  • c)2.3 and 12.0
  • d)2.3 and 3.0
Q.31
With a simple microscope, if the final image is located at the least distance of distinct vision form the eye placed close to the lens, then the magnifying power is
  • a) D/f
  • b) 1 +D/f
  • c)f/D
  • d)f×D
Q.32
With a simple microscope if the lens is held at a distance d from the eye and the image is formed at the least distance of distinct vision from the eye, then the magnifying power is
  • a) D/f
  • b) 1 + D/f
  • c) 1 + ( D - d)/f
  • d) 1 + ( D + d)/f
Q.33
The human eye has a lens which has a [ MPPMT 1994]
  • a)soft portion at its centre
  • b) hard surface
  • c)varying refractive index
  • d)constant refractive index
Q.34
If tube length of astronomical telescope is 105cm and magnifying power is 20 for normal setting, calculate the focal length of the objective [ AFMC 1994]
  • a) 100 cm
  • b) 10 cm
  • c)20 cm
  • d)25 cm
Q.35
A person wears glasses of power -2.5D. The defect of eye and far point of the person without the glasses are, respectively [ MPPMT 1995]
  • a) farsightedness, 40cm
  • b) nearsightedness, 40 cm
  • c)astigmatism, 40 cm
  • d)nearsightedness, 250 cm
Q.36
If a cloth of red colour is seen in the light of mercury vapour lamp, it will appear [ CPMT 1986]
  • a) Black
  • b) Red
  • c) Yellow
  • d) Blue
Q.37
An astronomical telescope has an angular magnification of magnitude 5 for distant objects. The separation between the objective and eye -piece is 36 cm and the final image is formed at infinity. the focal length fo of the objective and fe of the eye-piece are [ IIT 1989]
  • a) fo=45 cm and fe=-9 cm
  • b) fo=50 cm and fe=10 cm
  • c)fo=7.2 cm and fe=5 cm
  • d)fo=30 cm and fe=6 cm
Q.38
An achromatic combination is to be obtained using a convex and concave lens. The two lenses chosen should have [ MPPMT 1988]
  • a) Their powers equal
  • b) Their refractive indices equal
  • c)Their dispersive power equal
  • d)The product of their powers and dispersive powers equal
Q.39
A source emits light of wavelengths 4700Å, 5400Å and 6500Å. The light passes through red glass before being tested by a spectrometer. Which wavelength is seen in spectrum? [ PMT 1995]
  • a) 6500 Å
  • b) 6400 Å
  • c) 4700 Å
  • d) All the three above
Q.40
A person can not see the objects clearly placed at distances more than 40 cm. He is advised to use lens of power [ CPMT 1993]
  • a)-2.5D
  • b) +2.5D
  • c)-6.25D
  • d)+1.5D
Q.41
Spherical aberration in a thin lens can be reduced by [ IIT 1994]
  • a) using a monochromatic light
  • b) using a doublet combination
  • c)using a circular annular mask over the lens
  • d)increasing the size of the lens
Q.42
The focal length of the objective and eyepiece of a telescope are 100cm and 5cm respectively. Final image is formed at least distance of distinct vision. The magnification of telescope is [ Raj.PET 1997]
  • a) 20
  • b) 24
  • c)30
  • d)36
Q.43
The magnification produced by the objective lens and the eye lens of a compound microscope are 25 and 6 respectively. the magnifying power of this microscope is [ UGET 1995]
  • a) 19
  • b) 31
  • c) 150
  • d) √150
Q.44
A locality is photographed from an aeroplane flying at height of 2000 m with a camera whose focal length is 50cm. The ratio of linear size of the image to the size of the object, is nearly
  • a)1 : 10000
  • b) 1:40
  • c)1:4000
  • d)1:1000
Q.45
In a compound microscope, the focal lengths of objective and eye-lenses are 1.2 cm and 3cm respectively. If the object is put 1.25cm away from the objective lens and the final image is formed at infinity, the magnifying power of the microscope is
  • a) 150
  • b) 200
  • c)250
  • d)400
Q.46
In Young's experiment, monochromatic light is used to illuminate the two slits A and B. Interference fringes are observed on a screen placed in front of the slits. Now if a thin glass glass plate is placed normally in the pth of beam coming from the slit A, then [ MNR 1993]
  • a) The fringes will disappear
  • b) The fringe width will increase
  • c) The fringe width will decrease
  • d) There will be no change in fringe width
Q.47
A ray of light consisting of two wavelengths 4000Å and 5000Å falls from air on a quartz surface. the angle of incidence is 30°, and the indices of refraction for two wave lengths are respectively 1.47 and 1.The angle between the two refracted beams will be [ MPPMT 1993]
  • a)0°
  • b) 45°
  • c)90°
  • d)0.14°
Q.48
Motion of wave front of wave has direction with wave motion [ Raj.PMT 1997]
  • a) Parallel
  • b) Perpendicular
  • c)Opposite
  • d)At angle of θ
Q.49
If a plate of mica of thickness t and refractive index µ is introduced in the path of one of the coherent waves in interference experiment, the fringe pattern will shift by [ Raj.PMT 1997]
  • a)d(µ-1) /D
  • b) D(µ-1)t / d
  • c)d/ [(µ-1)D]
  • d) D(µ-1) / d
Q.50
In a Young's double slit experiment, the fringe width is found to be 0.4mm. If the whole apparatus is immersed in water of refractive index 4/3, without disturbing the geometrical arrangement, the new fringe width will be [ CBSE 1990]
  • a) 0.30 mm
  • b) 0.40mm
  • c) 0.53mm
  • d) 45 microns
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